KR102151012B1 - Method and apparatus for determining patterning process parameters - Google Patents

Abstract

A method of determining an overlay of a patterning process, the method comprising: obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell, wherein the unit cell has geometric symmetry at a nominal value of the overlay, and The representation is obtained by illuminating the substrate with a beam of radiation such that a beam spot on the substrate is filled with one or more physical instances of the unit cell; And determining a value of the first overlay for the unit cell, apart from the second overlay for the unit cell, also obtainable from the same optical property value, from the optical property value from the detected radiation representation, the Wherein the first overlay is in a different direction from the second overlay or between portions of the unit cell in a different combination than the second overlay.

Description

Method and apparatus for determining patterning process parameters

Cross-reference to related applications

This application is filed under U.S. Application Nos. 62/301,880 filed March 1, 2016-62/435,662 dated December 16, 2016, 62/435,670 dated December 16, 2016, 62/435,649 filed December 16, 2016. Claims priority to No. 62/435,630 dated December 16, 2016 and No. 62/458.932 dated February 14, 2017, which are incorporated herein by reference in their entirety.

The present invention relates to a method and apparatus for determining a parameter (e.g., an overlay) of a process for generating a pattern on a substrate, for example, wherein the determined parameter is to design, monitor, adjust, It can be used to do the same.

A lithographic apparatus is an apparatus that imparts a desired pattern on a substrate, usually on a target area of the substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs) or other devices designed to have functionality. In that case, a patterning device, also called a mask or reticle, can be used to create a circuit pattern to be formed on individual layers of a device designed to have functionality. Such a pattern may be transferred onto a target portion (eg, part of a die, including one or several dies) on a substrate (eg, a silicon wafer). The transfer of the pattern is typically performed through imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatuses include so-called steppers to which each target portion is irradiated by exposing the entire pattern onto the target portion at a time, and at the same time scanning a pattern through a radiation beam in a given direction ("scanning" direction). It includes a so-called scanner in which each target portion is irradiated by scanning the substrate in parallel or anti-parallel to. In addition, the pattern may be transferred from the patterning device to the substrate by imprinting the pattern on the substrate.

Fabricating a device, such as a semiconductor device, typically involves processing a substrate (eg, a semiconductor wafer) using several fabrication processes to form various features and often multiple layers of the device. Such layers and/or features are typically fabricated and processed using, for example, deposition, lithography, etching, chemical-mechanical polishing, and ion implantation. Multiple devices can be fabricated over multiple dies on a substrate and then divided into individual devices. This device manufacturing process can be considered a patterning process. The patterning process includes a pattern transfer step, such as optical and/or nanoinjection lithography using a lithographic apparatus, to provide a pattern on the substrate, and, typically but optionally, resist development by a developing apparatus, baking of the substrate using a bake tool, It involves one or more related pattern processing steps, such as etching the pattern by means of an etching apparatus. Furthermore, one or more metrology processes are involved in the patterning process.

The metrology process is used at various stages of the patterning process to monitor and/or control the process. For example, the metrology process can be used to measure one or more properties of the substrate, such as the relative position (e.g., registration, overlay, alignment, etc.) or dimensions (e.g., CD, line width, criticality, etc.) of features formed on the substrate during the patterning process. Dimensions, thickness, etc.), such that this performance of the patterning process can be determined from one or more of these properties. If one or more properties are unacceptable (e.g., outside a predetermined range for that property(s)), then one or more values of the patterning process, such that the substrate produced by the patterning process has acceptable property(s). It can be designed or modified based on, for example, measurements of one or more of these properties.

As lithography and other patterning process technologies advance, the dimensions of functional elements have continued to decrease, while the amount of functional elements, such as transistors per device, has continued to increase over several decades. On the other hand, the requirements for accuracy related to overlay, critical dimension (CD), etc. have become increasingly stringent. Errors such as errors in the overlay, errors in the CD, etc. will inevitably occur in the patterning process. Imaging errors may be caused by, for example, photoaberration, patterning device temperature rise, patterning device error, and/or substrate temperature rise, which may be characterized for example with respect to overlays, CDs, and the like. Additionally or alternatively, errors can be introduced into other parts of the patterning process, such as etching, developing, bake, etc., and characterized with respect to overlays, CDs, etc. similar to the previous case, for example. Errors can lead to problems with the functionality of the device, including failure of the device or one or more electrical problems of the device in operation.

Accordingly, it is desirable to take steps to characterize one or more of these errors and to design, modify, control, etc. the patterning process to reduce or minimize one or more of these errors.

In one embodiment, a first structure configured to be created by a first patterning process; And a second structure configured to be produced by the second patterning process, wherein the first structure and/or the second structure are not used to create a functional aspect of the device pattern, and the first and second structures The structures together form one or more instances of the unit cells, the unit cells having geometric symmetry in their nominal physical configuration, and the unit cells being the relative of the pattern placement in the first patterning process, the second patterning process and/or other patterning process In a physical configuration different from the nominal physical configuration due to the shift, it has a feature that causes asymmetry within the unit cell.

In one embodiment, a computer program product is provided comprising a non-transitory computer-readable medium having a data structure recorded thereon, the data structure corresponding to a metrology target as described herein. In one embodiment, a reticle comprising a pattern corresponding to a metrology target as described herein is provided.

In one embodiment, creating a first structure for the metrology target, the first structure will be created by a first patterning process that creates a corresponding device feature of the device; Creating a second structure for the metrology target-a second structure will be created by a second patterning process that creates a corresponding additional device feature of the device, wherein the first structure and the second structure are one of the unit cells. Forming instances of the above together, the unit cells having geometric symmetry in their nominal physical configuration; And introducing a feature into the metrology target that causes an asymmetry in a unit cell in a physical configuration different from the nominal physical configuration due to a relative shift of the position of the device feature in the device from the expected position of the device feature in the device. A method of incorporating is provided.

In one embodiment, a method is provided that includes measuring radiation redirected by metrology as described herein transferred to a substrate using a patterning process to determine a value of a parameter of the patterning process. In one embodiment, the parameters include overlay and/or edge placement errors.

In one aspect, a non-transitory computer program product is provided that stores machine-readable instructions for causing a processor to perform the above-described method. In an aspect, a computer program product is disclosed comprising a non-transitory computer-readable medium having instructions recorded thereon for implementing one or more process steps or a method described herein when executed by a computer.

In an aspect, a metrology device for measuring an object of a patterning process is provided, the metrology device configured to perform a method as described herein. In one aspect, an inspection apparatus for inspecting an object of a patterning process is provided, the inspection apparatus being configured to perform a method as described herein.

In one aspect, a metrology device configured to provide a beam of radiation to a surface of an object and detect radiation redirected by the structure at the surface of the object; And a computer program product as described herein. In one embodiment, the system further comprises a lithographic apparatus, the lithographic apparatus comprising: a support structure configured to hold the patterning device to modulate the radiation beam and a projection disposed to project the modulated beam onto the radiation sensitive substrate. Includes an optical system.

In one embodiment, a hardware processor system; And a non-transitory computer readable storage medium configured to store machine-readable instructions, wherein when executed, the machine-readable instructions cause the hardware processor system to cause the method as described herein. To perform.

The embodiments will now be described by way of example only with reference to the accompanying drawings:
1 schematically shows an embodiment of a lithographic apparatus;
2 schematically depicts an embodiment of a lithographic cell or cluster;
3A is a schematic diagram of a measuring device for use in measuring a target according to one embodiment, using a first pair of illumination apertures providing a specific illumination mode;
3B is a schematic detail of a diffraction spectrum of a target for a given direction of illumination;
3C is a schematic diagrammatic illustration of a second pair of illumination apertures that provide an additional illumination mode when using the measurement device for diffraction based overlay measurements;
3D is a schematic illustration of a third pair of illumination apertures combining a first pair and a second pair of apertures to provide an additional mode of illumination when using the measurement device for diffraction based overlay measurements;
4 schematically shows an overview of the shape of multiple grating targets (eg multiple gratings) and measurement spots on a substrate;
5 schematically shows an image of the target of FIG. 4 obtained in the apparatus of FIG. 3;
6 schematically illustrates an exemplary measurement device and metrology technique;
7 schematically shows an exemplary metrology device;
8 illustrates the relationship between an illumination spot of an inspection device and a metrology target;
9 schematically shows the process of deriving one or more variables of interest based on measurement data;
10A schematically illustrates an exemplary unit cell, an associated pupil representation, and an associated derived pupil representation;
10B schematically illustrates an exemplary unit cell, associated pupil representation, and associated derived pupil representation;
10C schematically depicts an exemplary target comprising one or more physical instances of a unit cell;
11 shows a high-level flow of obtaining weights for determining patterning process parameters from measured radiation;
12 shows a high level flow for determining patterning process parameters from measured radiation;
13 shows a high level flow of one embodiment of a data-driven technique;
14 shows a high level flow of one embodiment of a data-driven technique combined with a physical geometric model;
15 shows a high level flow of an embodiment of a data-driven technique combined with a physical geometric model;
16 shows a high level flow of one embodiment of a data-driven technique combined with a physical geometric model;
17 shows a high level flow of an embodiment of a data-driven technique combined with a physical geometric model;
18 schematically shows an embodiment of a target multiple overlay unit cell;
19 schematically shows an embodiment of a target multiple overlay unit cell;
20 shows an exemplary graph of two vectors corresponding to two different overlays;
21A and 21B schematically illustrate an example of a non-product target design;
22A, 22B, 22C and 22D schematically show examples of non-product target designs;
23A and 23B schematically illustrate an example of a non-product target design;
24A and 24B schematically illustrate an example of a non-product target design;
25A and 25B schematically illustrate an example of a non-product target design;
26A, 26B and 26C schematically illustrate an example of a non-product target design;
27A and 27B schematically illustrate an example of a non-product target design;
28A, 28B and 28C schematically illustrate an example of a non-product target design;
29A schematically shows an example of a device pattern feature;
29B, 29C, 29D and 29E schematically illustrate an example of steps in the device patterning process;
29F schematically shows an example of a structure of a non-product target design, corresponding to the steps of FIGS. 29B and 29D;
29G schematically illustrates an example of a non-product target design created from the structure of FIG. 29F;
30A schematically shows an example of a device pattern feature;
30B schematically shows an example of a structure of a non-product target design;
30C schematically shows an example of a non-product target design created from the structure of FIG. 30B;
31 corresponds to an embodiment of a method of designing a non-product target design; And
32 schematically shows a computer system capable of implementing an embodiment of the present invention.

Before describing the embodiments of the present invention in detail, it is beneficial to present an exemplary environment in which embodiments of the present invention may be implemented.

1 schematically depicts a lithographic apparatus LA. This device:

-An illumination system (illuminator) IL configured to modulate the radiation beam B (eg UV radiation or (EUV) radiation);

-A support structure (e.g., a support structure (e.g., a mask) connected to a first positioner (PM) configured to support the patterning device (e.g., a mask; MA) and configured to accurately position the patterning device according to a specific parameter Mask table; MT);

-A substrate table (e.g. wafer Table) (WT); And

-A projection system configured to project the pattern imparted to the radiation beam B to the target portion C of the substrate W (e.g. containing one or more dies) by the patterning device MA (e.g. A refractive projection lens system (PS), and the projection system is supported on the reference frame RF.

The lighting system can direct, shape, or control radiation of various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof. It may also include.

The support structure supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as, for example, whether the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or a table that can be fixed or movable as required. The support structure may ensure that the patterning device is in a desired position with respect to the projection system, for example. Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device".

The term “patterning device” as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a cross section of a radiation beam to create a pattern in a target portion of a substrate. In one embodiment, the patterning device is any device that can be used to impart a pattern in a cross section of a radiation beam to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may not exactly match the desired pattern at the target portion of the substrate, for example if the pattern comprises a phase shifting feature or a so-called assist feature. Be careful. In general, the pattern imparted to the radiation beam will correspond to a specific functional layer in the target portion, such as a device being created in an integrated circuit.

The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable (LCD) panels. Masks are well known in lithography and include mask types such as binary, alternating phase-shift, attenuating phase-shift, and various hybrid mask types. One example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incoming radiation beam in a different direction. The tilted mirror imparts a pattern in the radiation beam reflected by the mirror matrix.

As used herein, the term "projection system" is a refractive formula that is suitable for the exposure radiation being used or for other factors such as the use of an immersion liquid or the use of a vacuum. , Reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, should be broadly interpreted as including any type of projection system. In this specification, if the term "projection lens" is arbitrarily used, it may be regarded as having the same meaning as the more general term "projection system".

The projection system PS has an optical transfer function that may be non-uniform, which can affect the pattern imaged on the substrate W. For unpolarized radiation, this effect can be described very well by two scalar maps, which map the transmission (apodization) and relative phase (aberration) of the radiation out of the projection system PS. This scalar map, which may also be referred to as a transmission map and a relative phase map, may be expressed as a linear combination of a complete set of basic functions A particularly convenient set is the Zernike polynomials. ), which forms a set of orthogonal polynomials defined in the unit circle Determining each scalar map may involve determining the coefficients in this expansion. Zenike polynomials to be orthogonal on the unit circle Therefore, the Zenike coefficients may be determined by calculating the sequential dot product of the measured scalar map and each Zenike polynomial and dividing this by the square of the norm of the corresponding Zenike polynomial.

The transmission map and relative phase map are field and system dependent. That is, in general, each projection system PS will have a different Zenike evolution for each field point (ie for each spatial location in its image plane). The relative phase of the projection system PS in its pupil plane is, for example, from a source such as a point light source in the object plane of the projection system PS (i.e. the plane of the patterning device MA), the projection system PS ), and using a shearing interferometer to measure the wavefront (ie, the trajectory of points with the same phase). The shearing interferometer is a common path interferometer and therefore preferably, no secondary reference beam is required to measure the wavefront. The shearing interferometry is a pattern of interference in the projection system (i.e. a diffraction grating in the image plane of the substrate table (WT), e.g. a two-dimensional grid and a plane conjugate to the pupil plane of the projection system (PS). The interference pattern relates to a derivative of the phase of the radiation with respect to a coordinate in the pupil plane in the shearing direction The detector may be, for example, a charged coupled device (CCD). ) May also include an array of sensing elements.

The projection system PS of the lithographic apparatus may not produce a visible fringe, so the crystallization accuracy of the wavefront may be improved, for example, using a phase stepping technique, such as moving the diffraction grating. . Stepping may be performed in the plane of the diffraction grating and in a direction perpendicular to the scanning direction of the measurement. The stepping range may be one grating period, and at least three (evenly distributed) phase steps may be used. Thus, for example, three scanning measurements may be performed in the y-direction, and each scanning measurement is performed at a different position in the x-direction. This stepping of the diffraction grating effectively converts the phase fluctuation into an intensity fluctuation and allows the phase information to be determined. The grating may be stepped in a direction perpendicular to the diffraction grating (z direction) to calibrate the detector.

The transmission (apodization) of the projection system PS in its own pupil plane is from a source such as a point light source in the object plane of the projection system PS (i.e. the plane of the patterning device MA) It may be determined by projecting the radiation through the projection system PS, and measuring the intensity of the radiation in a plane that is conjugated to the pupil plane of the projection system PS using a detector. To determine the aberration, the same detector used to measure the wavefront may be used.

The projection system PS may include a plurality of light elements (e.g., lenses), and is configured to adjust one or more of the light elements to correct for aberrations (phase fluctuations across the pupil plane across the field). It may further include a mechanism (AM). To this end, the adjustment mechanism may be operable to manipulate one or more light elements (eg, lenses) within the projection system PS in one or more other ways. The projection system has a coordinate system, where its optical axis extension extends in the z direction. The adjustment mechanism includes: displacing one or more light elements; Tilt one or more optical elements; And/or modifying one or more light elements. The displacement of the optical element may be in any direction (x, y, z) or a combination thereof. Although rotation around the z-axis may be used for non-rotationally aspherical optical elements, by rotating around the axes in the x and/or y directions the optical element is typically out of the plane perpendicular to the optical axis. It is tilted. The deformation of the light element may include a low frequency shape (eg astigmatic and/or a high frequency shape (eg free shape aspherical surface). The deformation of the light, for example one or more faces of the light element) And/or by using one or more heating elements to heat one or more selected regions of the light element, and/or by using one or more actuators to exert a force on the apodization (transmission alteration across the pupil plane). It may not be possible to adjust the projection system PS in order to correct the) The transmission map of the projection system PS design the patterning device (e.g., a mask) MA for the lithographic apparatus LA. By using a computational lithography technique, the patterning device MA may be designed to at least partially correct apodization.

As shown, the device is transmissive (eg employing a transmissive mask). Alternatively, the device may be of a reflective type (eg, employing a programmable mirror array of the type as mentioned above, or employing a reflective mask).

The lithographic apparatus includes two (dual stage) or more tables (e.g., two or more substrate tables (WTa, WTb) under the projection system, with no substrate provided only to facilitate measurement, and/or cleaning, etc.). There may be more than one type of patterning device table, substrate table WTa and table WTb). In such a "multi-stage" machine, additional tables can be used in parallel, and preparation steps can be performed on one or more tables while one or more other tables are being used for exposure. For example, alignment measurement using the alignment sensor AS and/or level (height, tilt, etc.) measurement using the level sensor LS may be performed.

The lithographic apparatus may also be of a type in which at least a portion of the substrate can be covered by a liquid having a relatively high refractive index, such as water, to fill the space between the projection system and the substrate. The immersion liquid may also be applied to other spaces within the lithographic apparatus, such as between the patterning device and the projection system. Liquid immersion techniques are well known in the art to increase the numerical aperture of a projection system. The term “immersion” as used herein does not mean that a structure such as a substrate must be immersed in a liquid, rather it means that the liquid is positioned between the projection system and the substrate during exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. For example, if the radiation source is an excimer laser, the source and the lithographic apparatus may be separate entities. In these cases, the source is not considered to form part of the lithographic apparatus, and the radiation beam is, for example, the source SO ) To the fixture (IL). In other cases, for example, where the radiation source is a mercury lamp, this source may be an integrated component in the lithographic apparatus. The source SO and illuminator IL may be referred to as a radiation system together with a beam delivery system BD, if necessary.

The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. In general, at least the outer and/or inner radial extents (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illuminator IL can be adjusted. Additionally, the illuminator IL may include various other components such as an integrator IN and a confineer CO. An illuminator may be used to adjust the radiation beam to have a desired uniformity and intensity distribution in its cross section.

The radiation beam B is incident on the patterning device (eg, mask) MA held on the support structure (eg, mask table) MT, and is patterned by the patterning device. Crossing the patterning device MA, the radiation beam B passes through a projection system PS that focuses the beam on a target portion C of the substrate W. With the help of a second positioner (PW) and a position sensor (IF) (for example an interferometric measuring device, a linear encoder, a 2-D encoder or a capacitive sensor), for example, of the radiation beam B. In order to position the different target portions C in the path, the substrate table WT can be accurately moved. Similarly, the first positioner and the other position sensor (not clearly depicted in FIG. 1) are used for the path of the radiation beam B, for example after a mechanical search from the mask library or during a scan. It can be used to accurately position the patterning device MA. In general, the movement of the support structure MT may include a long-stroke module forming a part of the first positioner PM and a short-stroke module; Can also be realized using precise positioning). Likewise, the movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of the stepper (as opposed to the scanner), the support structure MT may be connected only to the short-stroke actuator, or may be fixed. The patterning device MA and the substrate W may be aligned using the patterning device alignment marks M1 and M2 and the substrate alignment marks P1 and P2. Although the substrate alignment marks occupy a dedicated target area as shown, they may be located in the space between the target areas (they are known as scribe-lane alignment marks). Likewise, if more than one die is provided in the mask MA, the mask alignment marks may be located between the dies.

The illustrated device may be used in one or more of the following modes:

1. In the step mode, while the support structure MT and the substrate table WT remain essentially stationary, the entire pattern imparted to the radiation beam is projected onto the target portion C at once (i.e. Single static exposure). Then, the substrate table WT is shifted in the (X) direction and/or (Y) direction so that different target portions C can be exposed. In the step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

2. In the scan mode, while the support structure MT and the substrate table WT are scanned synchronously, a pattern imparted to the radiation beam is projected onto the target portion C (ie, a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT may be determined by the magnification (reduction ratio) and image reversal characteristics of the projection system PS. In the scan mode, the maximum size of the exposure field limits the width of the target portion (in the unscanned direction) during a single dynamic exposure, while the length of the scanning motion determines the height of the target portion (in the scanning direction).

3. In another mode, while holding the programmable patterning device, the support structure MT remains essentially stationary, and the substrate table WT is kept while the pattern imparted to the radiation beam is projected onto the target area C. It is moved or scanned. In this mode, a generally pulsed radiation source is employed, and a programmable patterning device is updated as required, after each movement of the substrate table WT or between successive radiation pulses during a scan. . This mode of operation can be readily applied to maskless lithography using a programmable patterning device, such as a programmable mirror array of the type as mentioned above.

Further, combinations and/or variations of the above-described usage modes, or completely different usage modes may be employed.

As shown in Fig. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also referred to as a lithographic cell or cluster, which also includes an apparatus for performing pre-exposure and post-exposure processes on a substrate. do. Typically, such devices include one or more spin coaters (SC) for depositing one or more resist layers, one or more developer DE, one or more chill plates (CH) for developing the exposed resist, And at least one bake plate (BK). A substrate handler or robot (RO) picks up one or more substrates from the input/output ports (I/O1, I/O2), moves them between different process units, and then loads the lithographic apparatus's loading bay (LB). To pass on. These devices, collectively also referred to as tracks, are under the control of a track control unit (TCU), which is controlled by a supervisory control system (SCS), which also provides a lithography control unit (LACU). Control the device. Therefore, different devices can be operated to maximize throughput and processing efficiency.

In order for the substrate to be exposed by the lithographic apparatus to be accurately and consistently exposed, the exposed substrate is inspected and overlayed (this is, for example, between structures within the overlying layer or separately on that layer by, for example, a double patterning process). It is desirable to measure or determine one or more properties such as line width, critical dimension (CD), focal offset, material properties, and the like. Accordingly, the manufacturing facility in which the lysocell LC is located therein typically further includes a measurement system MET for accommodating a part or all of the substrate W processed in the lysocell. The metrology system MET may be the number of days of the lithographic apparatus LC, for example, may be part of the lithographic apparatus LA.

Measurement results can be provided directly or indirectly to a supervisory control system (SCS). If an error is detected, adjustments to the exposure of the subsequent substrate (especially if the inspection can be done early and fast enough so that one or more other substrates in the batch can still be exposed) and/or to the subsequent exposure of the exposed substrate are made. Can be done. In addition, substrates that have already been exposed may be stripped and reworked to improve yield, or discarded, thereby avoiding further processing on substrates known to be erroneous. If there is an error in only some target areas of the substrate, additional exposure may be performed only on the target areas considered good.

Within the metrology system MET, metrology devices are used to determine how one or more properties of a substrate, and specifically one or more properties of different substrates, or of different layers of the same substrate, vary from layer to layer. The metrology device may be integrated into the lithographic apparatus LA or the lithographic apparatus LC, or may be a standalone apparatus. In order to be able to make rapid measurements, it is preferred that the metrology device measures one or more properties in the exposed resist layer immediately after exposure. However, the latent image in the resist has a low contrast-in this case there is only a very small refractive index difference between the portion of the resist exposed to radiation and the portion not exposed to the radiation-all measuring devices make useful measurements of the latent image. Does not have sufficient sensitivity. Therefore, the measurement is performed after the post-exposure bake step (PEB), which is the first step typically performed on the exposed substrate and increases the contrast between the exposed and unexposed portions of the resist. Can be done. At this stage, the image in the resist may be referred to as a semi-latent image. It is also possible to measure the developed resist image after a pattern transfer step such as etching, at which point either the exposed or unexposed portions of the resist are removed. The latter possibility limits the possibility of reworking an erroneous substrate, but can still provide useful information.

To make metrology, one or more targets may be provided on the substrate. In one embodiment, the target is specifically designed and may include a periodic structure. In one embodiment, the target is a portion of a device pattern, for example a periodic structure of a device pattern. In one embodiment, the device pattern is a periodic structure of a memory device (eg, a structure such as a bipolar transistor (BPT), a bit line contact (BLC), etc.).

In one embodiment, the target on the substrate may include one or more 1-D periodic structures (e.g. gratings), which are printed such that after development periodic structural features are formed into solid resist lines. . In one embodiment, the target may comprise one or more 2-D structures (e.g. gratings), in which one or more periodic structures are formed as solid resist pillars or vias in the resist after development. It is printed as much as possible. Alternatively, the bars, pillars or vias may be etched into the substrate (eg, into one or more layers on the substrate).

In one embodiment, one of the parameters of interest in the patterning process is an overlay. The overlay can be measured using dark field scattering in which the zero order of diffraction (corresponding to the specular reflection) is blocked and only higher orders are processed. Examples of dark field measurements can be found in PCT Patent Application Publication Nos. WO 2009/078708 and WO 2009/106279, all of which are incorporated herein by reference. Additional examples of development of this technique have been described in US Patent Application Publication Nos. US2011-0027704, US2011-0043791 and US2012-0242970, all of which are incorporated herein by reference. A diffraction-based overlay using dark-field detection of diffraction order allows overlay measurements on smaller targets. These targets may be smaller than the illumination spot and may be surrounded by a device product structure on the substrate. In one embodiment, multiple targets may be measured in one radiation capture.

A metrology device suitable for use in an embodiment of the invention for measuring an overlay, for example, is schematically shown in FIG. 3A. The target T (including a periodic structure such as a grating) and the diffracted rays are shown in more detail in FIG. 3B. This measuring device may be a standalone device or it may be integrated into one of the lithographic apparatus LA, for example a measuring station, or a lithographic cell LC. The optical axis with several branches across the device is represented by a dotted line O. In such a device, the radiation emitted by the output 11 (e.g., a source such as a laser or xenon lamp or an opening connected to the source) is an optical system comprising lenses 12, 14 and an objective lens 16. Is directed to the substrate W through the prism 15. These lenses are arranged in a double sequence of 4F arrangement. Other lens devices may also be used as long as the substrate image is provided on the detector.

In one embodiment, the lens arrangement allows access to the intermediate pupil-plane for spatial-frequency filtering. Therefore, the angular range in which the radiation is incident on the substrate can be selected by defining the spatial intensity distribution in the plane that provides the spatial spectrum of the plane of the substrate, referred to herein as a conjugate pupil plane. In particular, for example this can be done by inserting an aperture plate 13 of a suitable shape between the lenses 12 and 14 in a plane which is a back-projected image of the objective lens pupil plane. . In the illustrated example, the aperture plate 13 has different shapes, named 13N and 13S, which allow different illumination modes to be selected. In this example, the lighting system forms an off-axis lighting mode. In the first illumination mode, the aperture plate 13N provides off-axis illumination from a direction designated as'north' for convenience of explanation only. In the second illumination mode, the aperture plate 13S is used to provide illumination coming from a direction similar but termed'south'. Using different apertures also enables different modes of lighting. It is desirable that the rest of the pupil plane is dark, as any unwanted radiation outside the desired illumination mode can interfere with the desired measurement signal.

As shown in FIG. 3B, the target T is disposed with a substrate W substantially normal to the optical axis O of the objective lens 16. A ray of light (I) striking the target (T) from an angle off-axis (O) causes a zero order ray (solid line 0) and two primary rays (dashed line +1 and double-chain line -1) to be generated. . In the case of the overfilled small target T, these rays are only one of many parallel rays covering the area of the substrate containing the metrology target T and other features. Since the aperture in the plate 13 has a finite width (the width necessary to allow a useful amount of radiation), the incident light I will in fact occupy a certain range of angles, and the diffracted rays 0 and + 1/-1 will spread to some extent. Depending on the small target's point spread function, each of the orders +1 and -1 will not be a single ideal ray as shown, but will spread more widely over a range of angles. Note that the periodic structure pitch and illumination angle can be designed or adjusted so that the primary ray entering the objective is aligned close to the central optical axis. The rays illustrated in FIGS. 3A and 3B are somewhat off-axis and are thus shown to be more easily distinguishable in the figure. At least 0 and +1 light rays of the rotation by the target on the substrate W are collected by the objective lens 16 and directed back to the prism 15.

Referring to FIG. 3A, both the first and second illumination modes are illustrated by designating opposite apertures named north (N) and south (S). When the incident ray I is incident from the north of the optical axis, that is, when the first illumination mode is applied using the aperture plate 13N, the +1 diffracted ray named +1(N) is applied to the objective lens 16 Join in. On the other hand, when the second illumination mode is applied when the aperture plate 13S is used, -1 diffracted ray (designated -1(S)) enters the lens 16. Thus, in one embodiment, the measurement results are, for example, after rotating the target to obtain the -1th and +1th diffraction order intensities separately, or after changing the illumination or imaging mode, placing the target under certain conditions. It is obtained by measuring times. Comparing these intensities for a given target provides a measure of the asymmetry in the target, and the asymmetry in the target can be used as an indicator of a lithographic process, for example an overlay. In the above-described situation, the lighting mode is changed.

The beam splitter 17 splits the diffracted beam towards two measurement branches. In the first measurement branch, the optical system 18 plots the diffraction spectrum (a pupil plane image) of the target on the first sensor 19 (e.g., a CCD or CMOS sensor) using the zero- and first-order diffracted beams. To form. Each diffraction order reaches a different point on the sensor, allowing the order to be compared and contrasted through image processing. The pupil plane image captured by the sensor 19 may be used to focus the metrology device and/or normalize the intensity measurements. Further, a pupil plane image may be used for many measurement purposes, such as reconstruction as described later in this specification.

In the second measurement branch, the optical system 20, 22 forms an image of the target on the substrate W in the sensor 23 (eg, a CCD or CMOS sensor). In the second measurement branch, an aperture stop 21 is provided in a plane that is conjugated with respect to the pupil-plane of the objective lens 16. The aperture stop 21 blocks the 0-th order diffracted beam so that the image of the target formed on the sensor 23 is formed by the -1 or +1 primary beam. Data related to the image measured by the sensors 19 and 23 are output to the image processor and controller PU, and their functions will vary according to the specific type of measurement being performed. Note that the term'image' is used broadly. An image of such periodic structure features (eg grid lines) would not be formed if only one of the -1 and +1 orders were present.

The specific forms of aperture plate 13 and stop 21 shown in FIG. 3 are purely examples only. In another embodiment, on-axis illumination of the target is used, and an aperture stop with an off-axis aperture is used to substantially deliver only one primary light of the diffracted radiation to the sensor. In another embodiment, secondary, tertiary, and higher-order beams (not shown in FIG. 3) may be used in the measurement instead of or in addition to the primary beam.

In order to allow the illumination to be adapted for these different types of measurements, the aperture plate 13 may include a plurality of aperture patterns formed around the rotating disk to reveal the desired pattern. Note that the aperture plate 13N or 13S is used to measure the periodic structure of the target oriented in one direction (X or Y depending on the set-up). In order to measure the orthogonal periodic structure, a method in which the target is rotated by 90° and 270° may be implemented. Other aperture plates are shown in FIGS. 3C and 3D. 3C illustrates two additional types of off-axis illumination modes. In the first illumination mode of Fig. 3C, the aperture plate 13E provides off-axis illumination from a direction designated'east' with respect to'north' described above for convenience of explanation only. In the second illumination mode of Fig. 3C, the aperture plate 13W is used to provide illumination coming from a similar, but termed'west' direction. 3D illustrates two additional types of off-axis illumination modes. In the first illumination mode of Fig. 3D, the aperture plate 13NW provides off-axis illumination from directions designated'north' and'west' as described above. In the second illumination mode, the aperture plate 13SE is similar but used to provide illumination from opposite directions, termed'south' and'east' as described above. This usage of the device and numerous other variations and applications are described, for example, in the previously published patent application publications mentioned above.

4 shows an exemplary composite metrology target T formed on the substrate W. The composite target comprises four periodic structures (gratings 32, 33, 34, 35 in this case) located close to each other. In one embodiment, the periodic structure layout can be made smaller than the measurement spot (ie, the periodic structure layout is overfilled). Thus, in one embodiment, the periodic structures are positioned close enough to each other so that they all lie within the measurement spot 31 formed by the illumination beam of the metrology device. In this case, all four periodic structures are simultaneously illuminated and imaged on the sensors 19 and 23 simultaneously. In one example specific to overlay measurements, the periodic structure 32, 33, 34, 35 itself is a complex periodic structure (e.g., a complex lattice) formed by overlying periodic structures, i.e., the periodic structures are the substrate Patterned in different layers of the device formed on (W) such that at least one periodic structure in one layer is overlaid on at least one periodic structure in another layer. Such targets may have external dimensions within 20 μm x 20 μm or within 16 μm x 16 μm. Furthermore, all of the periodic structures are used to measure the overlay between a particular pair of layers. To allow the target to measure more than one pair of layers, the periodic structures 32, 33, 34, 35 are biased differently to facilitate the measurement of the overlay between the different layers in which different portions of the complex periodic structures are formed. Can have an overlaid offset. Thus, all of the periodic structures for a target on the substrate will be used to measure one pair of layers, all of the periodic structures for another same target on the substrate will be used to measure another pair of layers, and different biases Makes it easier to distinguish between layer pairs.

Returning to FIG. 4 again, the periodic structures 32, 33, 34, 35 may have different orientations as shown, so as to diffract incoming radiation in the X and Y directions. In one example, periodic structures 32 and 34 are X-direction periodic structures with biases of +d, -d, respectively. The periodic structures 33 and 35 may be Y-direction periodic structures with offsets +d and -d, respectively. While four periodic structures are illustrated, other embodiments may include larger matrices to achieve the desired accuracy. For example, a 3 x 3 array of nine complex periodic structures may have biases -4d, -3d, -2d, -d, 0, +d, +2d, +3d, +4d. Individual images of these periodic structures can be identified in the image captured by the sensor 23.

5 shows an example of an image that is formed on the sensor 23 and can be detected by the sensor using the target of FIG. 4 in the apparatus of FIG. 3 and using the aperture plate 13NW or 13SE of FIG. 3D. Shows. While sensor 19 cannot disassemble individual other periodic structures 32-35, sensor 23 is possible. The dark square is the field of the image on the sensor, in which the illuminated spot 31 on the substrate is imaged into the corresponding circular area 41. In this case, rectangular regions 42-45 represent images of periodic structures 32-35. The target may be positioned between device product features, not within or in addition to the scribe lane. If periodic structures are located in the device product area, the device product feature can also be seen around this image field. The processor and controller PU processes these images using pattern recognition to identify distinct images 42-45 of periodic structures 32-35. In this way, the images do not have to be aligned very precisely at a specific location within the sensor frame, which greatly improves the throughput of the measurement device as a whole.

Once an individual image of periodic structures is identified, the intensity of that individual image can be measured, for example by averaging or summing selected pixel intensity values within the identified area. The intensity and/or other attributes of the image can be compared to each other. These results can be combined to measure other parameters of the lithographic process. Overlay performance is an example of this parameter.

In one embodiment, one of the parameters of interest in the patterning process is the feature width (eg CD). 6 shows a highly schematic exemplary metrology device (eg, scatterometer) capable of enabling feature width determination. It includes a broadband (white light) radiation projector 2 that projects radiation onto a substrate W. The redirected radiation is delivered to a spectrometer detector 4, which measures a spectrum 10 (intensity as a function of wavelength) of specularly reflected radiation, for example as shown in the graph at the bottom left. From these data, for example, by Rigorous Coupled Wave Analysis and non-linear regression, or with a library of simulated spectra as shown in the lower right of FIG. 6. By comparison, the structure or profile resulting in the detected spectrum may be reconstructed by the processor (PU). In general, for reconstruction, the overall shape of the structure is known and some variables are estimated from information about the process of manufacturing these structures, leaving only a few variables of these structures to be determined from the measured data. Such a measuring device may be configured as a normal-incidence measuring device or an oblique-incidence measuring device. Furthermore, in addition to the measurement of parameters through reconstruction, angular resolved scattering measurements are useful for measuring asymmetry of features in products and/or resist patterns. A specific application of the asymmetry measurement is for the measurement of overlays, in which case the target comprises a set of periodic features that are superimposed on each other. The concept of asymmetric measurement in this manner is described, for example, in US Patent Publication No. US2006-066855, which is incorporated herein in its entirety.

7 shows an example of a metrology device 100 suitable for use in an embodiment of the invention disclosed herein. The principle of operation of this type of metrology device is described in more detail in US Patent Application Nos. US 2006-033921 and US 2010-201963, which are incorporated herein by reference in their entirety. The optical axis with several branches across the device is represented by a dotted line O. In such a device, the radiation emitted by the source 110 (e.g., a xenon lamp) is the lens system 120, the aperture plate 130, the lens system 140, the partially reflective surface 150, and the objective. It is directed onto the substrate W by an optical system comprising a lens 160. In one embodiment, these lens systems 120, 140, 160 are arranged in a double sequence of 4F arrangement. In one embodiment, radiation emitted by radiation source 110 is collimated using lens system 120. Different lens arrangements can be used if desired. The angular range in which the radiation is incident on the substrate can be selected by defining a spatial intensity distribution in the plane that provides a spatial spectrum of the substrate plane. In particular, this can be done by inserting an opening plate 130 of a suitable shape between the lenses 120 and 140 in the plane which is the back-projected image of the objective lens pupil plane. Different intensity distributions (eg, annular, dipole, etc.) are possible with different apertures. The angular distribution of illumination in the radial and peripheral directions, and properties such as the wavelength, polarization and/or coherency of the radiation can all be adjusted to achieve the desired result. For example, one or more interference filters 130 (see FIG. 9) are used to select a wavelength of interest in the range of 400-900 nm or less, such as 200-300 nm. ) Can be provided between. The interference filter may be tunable rather than including a different set of filters. Instead of an interference filter, a grating can be used. In one embodiment, one or more polarizers 170 (see FIG. 9) may be provided between the source 110 and the partially reflective surface 150 to select the polarization of interest. The polarizer may not contain different sets of polarizers but may be tunable.

As shown in FIG. 7, the target T is disposed together with the substrate W forming a normal line to the optical axis O of the objective lens 160. Accordingly, the radiation from the source 110 is reflected by the partial reflective surface 150 and through the objective lens 160 to the spot S (see FIG. 8) on the target T on the substrate W. It is focused. In one embodiment, the objective lens 160 preferably has a high numerical aperture (NA) of at least 0.9 or at least 0.95. Even immersion metering devices (using relatively high refractive index fluids such as water) may have a numerical aperture of greater than (1).

The rays of lights 170 and 172 that are focused from an angle off axis O to the illumination spot generate diffracted rays 174 and 176. It should be remembered that these rays are only one of many parallel rays that cover the area of the substrate containing the target T. Each element within the illumination spot is within the visible range of the metrology device. Since the aperture in the plate 130 has a finite width (the width necessary to allow a useful amount of radiation), the incident rays 170 and 172 will in fact occupy a certain range of angles, and the diffracted rays ( 174, 176) will spread to some extent. Depending on the small target's point spread function, each diffraction order will not be a single ideal ray as shown, but will spread more widely over a range of angles.

At least the 0th order diffracted by the target on the substrate W is condensed by the objective lens 160 and is directed not through the partial reflection surface 150. Optical element 180 provides at least a portion of the diffracted beam to optical system 182, which system uses a zero-order and/or first-order diffracted beam to provide a sensor 190 (e.g., a CCD or CMOS sensor). A diffraction spectrum (a pupil plane image) of the target is formed on the image. In one embodiment, an aperture 186 is provided such that a specific diffraction order is provided to the sensor 190 by filtering out a specific diffraction order. In one embodiment, aperture 186 causes substantially or primarily zero-order radiation to reach sensor 190. In one embodiment, the sensor 190 may be a two-dimensional detector so that the two-dimensional angular scattering spectrum of the substrate target T can be measured. The sensor 190 may be, for example, an array of CCD or CMOS sensors, and may use an integration time of 40 ms per frame, for example. The sensor 190 may be used to measure the intensity of the redirected radiation at a single wavelength (or a narrow wavelength range), may separately measure the intensity at multiple wavelengths, or measure the intensity integrated over a certain wavelength range. You can also measure it. In addition, the sensor may individually measure the intensity of radiation with transverse magnetic-polarized and transverse electric-polarized radiation, and/or the phase difference between transverse magnetic-polarized radiation and transverse electric-polarized radiation. have.

Alternatively, the optical element 180 provides at least a portion of the diffracted beam to the measurement branch 200 to form an image of the target on the substrate W on the sensor 230 (eg, a CCD or CMOS sensor). The measurement branch 200 includes various auxiliary functions such as focusing the measurement device (i.e., allowing the substrate W to be in focus with the objective lens 160), and/or dark field imaging of the type mentioned in the introduction. Can be used for.

To provide a customized viewing range for different sizes and shapes of the grating, an adjustable field stop 300 provides a path from source 110 to objective lens 160 within lens system 140. The field stop 300 has an aperture 302 and is located in a plane that is conjugated with the plane of the target T, so that the illumination spot becomes the image of the aperture 302. The image can be scaled according to the magnification factor, or the aperture and illumination spot can have a 1:1 size relationship. In order to allow the illumination to be adapted for different types of measurements, the aperture plate 300 may include a plurality of aperture patterns formed around the rotating disk to reveal the desired pattern. Alternatively or additionally, a set of plates 300 may be provided and swarped to achieve the same effect. Additionally or alternatively, programmable aperture devices such as deformable mirror arrays or transmissive spatial light modulators may also be used.

Typically, the target will be aligned with its periodic structure features arranged parallel to the Y axis or parallel to the X axis. As for its diffraction behavior, a periodic structure with features extending in a direction parallel to the Y axis has periodicity in the X direction, whereas a periodic structure with features extending in a direction parallel to the X axis has a periodic structure in the Y direction. Have periodicity. In order to measure performance in both directions, both types of features are provided collectively. For brevity it will be referred to as lines and spaces, but the periodic structure need not consist of lines and spaces. Moreover, each line and/or the space between the lines may be a structure formed of smaller sub-structures. Furthermore, the periodic structure may be formed with periodicity in two dimensions at once, for example, when the periodic structure includes posts and/or via holes.

FIG. 8 shows a top view of a typical target T, and an illumination spot S in the apparatus of FIG. 7. In order to obtain a diffraction spectrum free of interference from surrounding structures, in one embodiment target T is a periodic structure (eg grating) that is larger than the width (eg diameter) of the illumination spot S. The width of the spot S may be smaller than the width and length of the target. In other words, the target is'underfilled' by illumination, and the diffraction signal is essentially free of signals from product features or the like outside the target itself. Through this, the target can be easily reconstructed mathematically so that the target can be regarded as infinite.

9 schematically depicts an exemplary process for determining the value of one or more variables of interest in a target pattern 30' based on measured data obtained using metrology. Radiation detected by detector 190 provides a measured radiation distribution 108 for target 30'.

For a given target 30', the radiation distribution 208 can be calculated/simulated from a parameterized mathematical model 206', for example using a numerical Maxwell solver 210. The parameterized mathematical model 206 shows exemplary layers of various materials that make up the target and are associated with the target. The parameterized mathematical model 206 may include one or more of the variables for some of the layers and features of the target under consideration, which may be modified and derived. As shown in Figure 9, one or more of the variables are the thickness t of one or more layers, the width w of one or more features (e.g., CD), the height h of the one or more features, the sidewall angle α of the one or more features, and And/or may include the relative position of features (referred to herein as overlays). Although not shown, one or more of the variables are the refractive index of one or more of the layers (e.g., real or complex refractive index, refractive index tensor, etc.), the extinction coefficient of one or more layers, absorption of one or more layers, resist loss during development, one It may further include footing of more than one feature and/or line edge roughness of one or more features, but is not limited thereto. One or more values of one or more parameters of the 1-D periodic structure or of the 2-D periodic structure, such as the value of the width, length, shape or 3-D profile characteristics, are obtained from knowledge of the patterning process and/or other measurement processes and reconstructed. Can be entered into the process. For example, the initial value of the variable may be such an expected value of one or more parameters for the target being measured, such as the value of CD, pitch, etc.

In some cases, the target may be divided into multiple instances of a unit cell. In order to help easily calculate the radiation distribution of the target in such a case, the model 206 can be designed to calculate/simulate using the unit cells of the target's structure, which unit cells are repeated as instances across the entire target. Thus, to determine the radiation distribution of the target, the model 206 calculates using one unit cell and copies the result to fit the entire target using appropriate boundary conditions.

In addition to or alternatively to calculating the radiation distribution 208 at the time of reconstruction, a plurality of radiation distributions 208 are pre-calculated for a plurality of fluctuations of the variable of the target portion to be considered, and a library of radiation distributions to be used at the time of reconstruction is prepared. Can be generated.

The measured radiation distribution 108 is then compared to the radiation distribution 208 calculated at 212 (calculated close to that point or obtained from the library) to determine the difference between them. If there is a difference, the values of one or more of the variables of the parameterized mathematical model 206 can be changed, and the newly calculated radiation distribution 208 is sufficient between the measured radiation distribution 108 and the radiation distribution 208. It is obtained (calculated or obtained from the library) and compared against the measured radiation distribution 108 until a match exists. At that point, the values of the parameters of the parameterized mathematical model 206 provide a good or best match to the geometry of the actual target 30'. In one embodiment, a sufficient match exists if the difference between the measured radiation distribution 108 and the calculated radiation distribution 208 falls within the tolerance threshold.

In such a measuring device, a substrate support may be provided for holding the substrate W during the measuring operation. The substrate support may be similar or identical to the substrate support WT of FIG. 1 in shape. In one example in which the metrology apparatus is integrated with the lithographic apparatus, this may be the same substrate table. Coarse positioners and precision positioners can be configured to accurately position the substrate relative to the measurement optical system. Various sensors and actuators are provided, for example to obtain the position of a target of interest and bring it to a position under the objective lens. Typically, many measurements will be made to the target at different locations across the substrate W. The substrate support can be moved in the X and Y directions to obtain different targets, and the substrate support can be moved in the Z direction to obtain the desired position of the target with respect to the focus of the optical system. For example, if the optical system remains substantially stationary (usually in the X and Y directions, but can also be stopped in the Z direction) and only the substrate moves, the objective lens moves to a different position relative to the substrate. It is convenient to understand and explain the behavior as it is being done. If the relative position of the substrate and the optical system is correct, which of them is actually moving, or whether both are moving, or a combination of some of the optical systems is moving (e.g. in the Z and/or tilt direction) It is not theoretically important whether the rest of the optical system is stationary and the substrate is moving (eg, in the X and Y directions, but optionally also in the Z and/or tilt directions).

In one embodiment, the measurement accuracy and/or sensitivity of the target is one or more properties of the beam of radiation provided on the target, e.g., the wavelength of the radiation beam, the polarization of the radiation beam, the intensity distribution of the radiation beam (i.e., angle or Spatial intensity distribution), etc. Thus, for example, a specific measurement strategy can be selected that can obtain good measurement accuracy and/or sensitivity of the target.

To monitor a patterning process (e.g., a device manufacturing process) comprising at least one pattern transfer step (e.g., a photolithography step), the patterned substrate is inspected and one or more parameters of the patterned substrate are measured/ Is determined. One or more parameters may be, for example, overlays between successive layers formed in or on the patterned substrate, for example critical dimensions (CD) of features formed in or on the patterned substrate (e.g., critical line width), light It may include a focus or focus error in a lithography step, a dose or dose error in an optical lithography step, a photo aberration in an optical lithography step, an arrangement error (eg, edge placement error), and the like. Such measurements can be performed on the product substrate itself and/or on a dedicated metrology target provided on the substrate. The measurement can be performed after development of the resist but before etching or may be performed after etching.

In one embodiment, the parameters obtained from the obtained measurement process are parameters derived from parameters determined directly from the measurement process. As an example, the derived parameter obtained from the measurement parameter is the edge placement error for the patterning process. The edge placement error causes the position of the edge of the structure created by the patterning process to be different. In one embodiment, the edge placement error is derived from the overlay value. In one embodiment, the edge placement error is derived from a combination of an overlay value and a CD value. In one embodiment, the edge placement is derived from values of overlay values, CD values, and local variations (eg, edge roughness of individual structures, shape asymmetry, etc.). In one embodiment, the edge placement error includes the extreme value of the combined overlay and CD errors (eg, 3 standard deviations, ie 3σ). In one embodiment, in a multi-patterning process that involves creating a structure, and that involves "cutting" a structure by removing a portion of the structure through etching of a pattern provided by a patterning process relative to the structure, The edge placement error takes the form (or includes one or more of the following terms):

, 여기에서 σ는 표준 편차이고,

는 오버레이의 표준 편차에 대응하며,

는 패터닝 프로세스에서 생성된 구조체의 임계 치수 균일성(CDU)의 표준 편차에 대응하고,

는 존재한다면 패터닝 프로세스에서 생성된 절삭부의 임계 치수 균일성(CDU)의 표준 편차에 대응하며,

는 광학적 근접성 효과(OPE) 및/또는 레퍼런스 CD에 대한 피치에서의 CD의 차이인 및/또는 근접성 바이어스 평균(PBA)의 표준 편차에 대응하고,

는 선 에지 거칠기(LER) 및/또는 로컬 배치 오차(LPE)의 표준 편차에 대응한다. 위의 수식이 표준 편차에 관련되지만, 이것은 분산과 같은 다른 비견할만한 통계 방식으로 공식화될 수 있다.

, Where σ is the standard deviation,

Corresponds to the standard deviation of the overlay,

Corresponds to the standard deviation of the critical dimension uniformity (CDU) of the structure produced in the patterning process,

If present, corresponds to the standard deviation of the critical dimension uniformity (CDU) of the cut produced in the patterning process,

Corresponds to the optical proximity effect (OPE) and/or the standard deviation of the proximity bias mean (PBA), which is the difference of the CD in pitch relative to the reference CD, and

Corresponds to the standard deviation of the line edge roughness (LER) and/or local placement error (LPE). Although the above formula relates to the standard deviation, it can be formulated in other comparable statistical ways, such as variance.

Various techniques exist for measuring structures formed in the patterning process, including using a scanning electron microscope, an image-based measurement tool, and/or a variety of specialized instruments. As described above, a special metrology tool of a fast and non-invasive form is that a beam of radiation is directed onto a target on a substrate surface and the properties of the scattered (diffracted/reflected) beam are measured. By evaluating one or more of the properties of the radiation scattered by the substrate, one or more properties of the substrate may be determined. This can be termed diffraction-based metrology. One application of such diffraction-based metrology is the field of measurement of feature asymmetry within a target. This can be used, for example as the size of the overlay, but other applications are also known. For example, asymmetry can be measured by comparing opposite portions of the diffraction spectrum (eg, by comparing the -1 order and +1 order in the diffraction spectrum of a periodic grating). This can be done simply as described above and, for example, as described in US Patent Application Publication No. US2006-066855, the entire contents of which are incorporated herein by reference. Another application of such diffraction-based metrology is the field of measuring features within a target. Such a technique can use the apparatus and method described above with reference to FIGS. 6-9.

Now, while this technique is effective, it is desirable to provide a new measurement technique that induces feature asymmetry in the target (eg overlay, CD asymmetry, sidewall angle asymmetry, etc.). This technique may be effective for specially designed metrology targets or more importantly to directly determine feature asymmetry on the device pattern.

Referring to Fig. 10, the principle of this measurement technique is described in the context of an overlay embodiment. In Fig. 10A, the geometrically symmetric unit cell of the target T is shown. The target T may include only one physical instance of the unit cell or may include a plurality of physical instances of the unit cell as shown in FIG. 10C.

The target T may be a specially designed target. In one embodiment, the target is a scribe lane. In one embodiment, the target is an in-die target, ie the target is between device patterns (and thus between scribe lanes). In one embodiment, the target may have a feature width or pitch similar to the device pattern feature. For example, the target feature width or pitch is 300% or less of the minimum feature size or pitch of the device pattern, 200% or less of the minimum feature size or pitch of the device pattern, 150% or less of the minimum feature size or pitch of the device pattern, or It may be 100% or less of the minimum feature size or pitch of the device pattern.

The target T may be a device structure. For example, target T may be part of a memory device (often having one or more structures that may be geometrically symmetrical or symmetrical as described below).

In one embodiment, the target (T) or physical instance of the unit cell is an area of 2400 microns squared or less, an area of 2000 microns squared or less, an area of 1500 microns squared or less, an area of 1000 microns squared or less, an area of 400 microns squared or less , Area less than 200 microns square, area less than 100 microns square, area less than 50 microns square, area less than 25 microns square, area less than 10 microns square, area less than 5 microns square, area less than 1 micron square, It can have an area of less than 0.5 microns squared, or less than 0.1 microns squared. In one embodiment, the target (T) or physical instance of the unit cell is 50 microns or more, 30 microns or more, 20 microns or more, 15 microns or more, 10 microns or more, 5 microns or more, 3 microns or more parallel to the plane of the substrate. , 1 micron or more, 0.5 micron or more, 0.2 micron or more, or 0.1 micron or more, micron or more, micron or more cross-sectional dimensions.

In one embodiment, the target (T) or physical instance of the unit cell is 5 microns or less, 2 microns or less, 1 micron or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 150 nm or less , 100 nm or less, 75 nm or less, 50 nm or less, 32 nm or less, 22 nm or less, 16 nm or less, 10 nm or less, 7 nm or less, or 5 nm or less.

In one embodiment, the target T has a plurality of physical instances of the unit cell. Thus, the target T may typically have the higher dimensions listed here, but the physical instance of the unit cell will have the lower dimensions listed here. In one embodiment, the target T is 50,000 physical instances of a unit cell, 25,000 physical instances of a unit cell, 15,000 physical instances of a unit cell, 10,000 physical instances of a unit cell, 5,000 physical instances of a unit cell, Includes 1000 physical instances of a unit cell, 500 physical instances of a unit cell, 200 physical instances of a unit cell, 100 physical instances of a unit cell, 50 physical instances of a unit cell, or 10 physical instances of a unit cell. do.

Preferably, a physical instance of a unit cell or a plurality of physical instances of a unit cell collectively fills the beam spot of the metrology device. In such cases, the measured results essentially contain only information obtained from physical instances of the unit cell (or multiple instances thereof). In one embodiment, the beam spot has a cross-sectional width of 50 microns or less, 40 microns or less, 30 microns or less, 20 microns or less, 15 microns or less, 10 microns or less, 5 microns or less, or 2 microns or less.

The unit cell of FIG. 10A includes at least two structures to be instantiated or physically instantiated on a substrate. The first structure 1000 includes a line and the second structure 1005 includes an elliptical shape. Of course, the first and second structures 1000 and 1005 may be structures different from those shown.

Furthermore, in this example, in order to have an error in the overlay, there may be a relative shift from their expected position between the first structure and the second structure 1000, 1005 because they are individually transferred onto the substrate. In this example, the first structure 1000 is located in a higher layer on the substrate than the second structure 1005. Thus, in one embodiment, the second structure 1005 may be created in the first lower layer upon the first execution of the patterning process, and the first structure 1000 may be created on the second execution of the patterning process. It can be created in a second higher layer than a lower layer. Now, the first and second structures 1000 and 1005 need not be located in different layers. For example, in a double patterning process (including, for example, an etching process as part of it), the first and second structures 1000, 1005 may be created in the same layer to form essentially a single pattern, but the same There may still be "overlay" problems with respect to their relative placement within the layer. In this single layer example, both the first and second structures 1000 and 1005 have the shape of a line as shown in FIG. 10A with respect to the first structure 1000, for example, but the first pattern transfer The line of the second structure 1005 already provided on the substrate in the process may be interleaved with the line of the structure 1000 provided in the second pattern transfer process.

It is important that the unit cell has or can have geometric symmetry about an axis or point. For example, the unit cell of FIG. 10A has, for example, an axis 1010 and a reflective symmetry about a point / eg a rotational symmetry about a point 1015. Similarly, the physical instance of the unit cell of FIG. 10C (and thus the combination of the physical instances of the unit cell) has geometric symmetry.

In one embodiment, the unit cell has geometric symmetry with respect to certain features (eg overlays). Embodiments of the present invention focus on unit cells with zero overlay when geometrically symmetric. However, instead, the unit cell may have a zero overlay for certain geometric asymmetry. Then, an appropriate offset and calculation will be used to account for the unit cell with zero overlay if it has a specific geometric asymmetry. Suitably, the unit cell should be able to change its symmetry depending on the value of a particular feature (e.g., it can be asymmetrical, more asymmetric, or symmetrical from an asymmetric situation).

In the example of FIG. 10A, the unit cell has geometric symmetry with respect to a zero overlay (it need not be a zero overlay). This is represented by arrows 1020 and 1025 indicating that the lines of the first structure 1000 are evenly aligned with the elliptical shape of the second structure 1005 (at least a partial alignment unit cell is shown in FIG. To have geometric symmetry as shown). Therefore, in this example, if the unit cell has geometric symmetry, there is a zero overlay. However, if there is an error in the overlay (e.g., non-zero overlay), the unit cell is no longer geometrically symmetric, and by definition the target is no longer geometrically symmetric.

Furthermore, when the target includes a plurality of physical instances of the unit, the instances of the unit cell are periodically deployed. In one embodiment, instances of the unit cell are placed in a lattice. In one embodiment, the periodic arrangement has geometric symmetry within the target.

Therefore, in this technique, as will be discussed further from now on, feature asymmetries of interest (e.g., non-zero overlays) can determine feature asymmetry (e.g., non-zero overlays). The advantage of being (eg, a change to geometric asymmetry, or a change to additional geometric asymmetry, or from geometric asymmetry to geometric symmetry) arises.

A target comprising a physical instance of the unit cell of FIG. 10A may be illuminated with radiation, for example using the metrology device of FIG. 7. The radiation redirected by the target may be measured by the detector 190, for example. In one embodiment, the pupil of the redirected radiation, ie the Fourier transform plane, is measured. An exemplary measurement of this pupil is shown as a pupil image 1030. The pupil image 1030 has a diamond shape, but does not have to have this shape. The terms pupil and pupil plane herein include any conjugation of them except where the context does not (eg, where the pupil plane of a particular optical system is being identified). The pupil image 1030 is an image defined for the optical properties (intensity in this case) of the pupil of the substantially redirected radiation.

For convenience, the discussion herein will focus on intensity as an optical property of interest. However, the techniques of the present invention may also be used with one or more alternative or additional optical properties, such as phase and/or reflectivity.

Furthermore, for convenience, the discussion herein focuses on detecting and processing images of redirected radiation, in particular pupil images. However, the optical properties of redirected radiation can be measured and expressed in a way other than an image. For example, redirected radiation may be processed for one or more spectra (eg, intensity as a function of wavelength). Thus, the detected image of the redirected radiation can be regarded as an example of an optical representation of the redirected radiation. Therefore, in the case of a pupil plane image, the pupil image is an example of a pupil expression.

Furthermore, the redirected radiation can be polarized or non-polarized. In one embodiment, the measurement beam radiation is polarized radiation. In one embodiment, the measurement beam radiation is linearly polarized.

In one embodiment, the pupil representation is primarily, or substantially, one diffraction order of the redirected radiation from the target. For example, the radiation may be 80% or more, 85% or more, 90% or more, 95% or more, 98% or more, or 99% or more of a specific order of radiation. In one embodiment, the pupil representation is primarily, or substantially, for zero-order redirected radiation. This may occur, for example, if the pitch of the target, the wavelength of the measurement radiation, and optionally one or more other conditions causes the target to redirect zero-order radiation (although one or more higher orders may exist) as a principal component. I can. In one embodiment, most of the pupil representation is zero-order redirected radiation. In one embodiment, the pupil representation is for the zero order radiation and separately for the primary radiation, which can then be linearly combined (superimposed). The aperture 186 of FIG. 7 can be used to select a specific order of radiation, for example the zero order.

With respect to the pupil image 1030 corresponding to the geometrically symmetric unit cells of the first and second structures 1000, 1005, the intensity distribution is essentially symmetric within the pupil image (e.g., the same symmetry as the geometric structure). Has a type). This is also confirmed by removing portions of the symmetrical intensity distribution from the pupil image 1030, resulting in a derived pupil image 1035. In order to remove the symmetrical intensity distribution part, a specific pupil image pixel (for example, a pixel) is a symmetrical intensity removed by subtracting the intensity of the symmetrically positioned pupil image pixel from the intensity of that specific pupil image pixel. It can have a distribution part, and vice versa. In one embodiment, a pixel may correspond to a pixel of a detector (eg, detector 190), but it does not have to; For example, the pupil image pixel may be a plurality of pixels of the detector. In one embodiment, the symmetry point or axis of symmetry over which the pixel intensity is subtracted corresponds to the symmetry point or axis of symmetry of the unit cell. Therefore, for example, considering the pupil image 1030, the symmetric intensity distribution part is located symmetrically from the intensity (Ii) at the specific pixel displayed, that is, symmetrically about the axis 1032 It can be eliminated by subtracting the intensity (Ii') from the pixel. Thus, the intensity Si from which the symmetric intensity part in a particular pixel has been removed is now Si = Ii-Ii'. This may be repeated for a plurality of pixels of the pupil image, for example all pixels in the pupil image. As can be seen in the derived pupil image 1035, the intensity distribution corresponding to the symmetric unit cell is essentially completely symmetric. Thus, a symmetric target having a symmetric unit cell geometry (and, if applicable, a specific periodicity of an instance of the unit cell) results in a symmetric pupil response as measured by the metrology device.

Referring now to FIG. 10B, an example of an error in the overlay is shown for the unit cell shown in FIG. 10A. In this case, the first structure 1000 is shifted in the X-direction with respect to the second structure 1005. In particular, the axis 1010 centered on the line of the first structure 1000 has been shifted right to the axis 1045 in FIG. 10B. Thus, the overlay 1040 has an X-direction error; That is, there is an overlay error in the X direction. Of course, the second structure 1005 may be shifted relative to the first structure 1000, or both may be shifted relative to each other. In any case, the result is an X-direction overlay error. However, as can be understood from this unit cell arrangement, a pure relative shift in the Y-direction between the first structure 1000 and the second structure 1005 will not change the geometric symmetry of this unit cell. However, if the geometric arrangement is appropriate, the overlay in two directions or between portions of different combinations of unit cells can change the symmetry and can also be determined as described further below.

The result of the change in the physical configuration of the unit cell from the nominal physical configuration, represented by the error of the overlay 1040 in FIG. 10A, is that the unit cell has become geometrically asymmetric. This may be indicated by arrows 1050 and 1055 of different lengths, which show that the elliptical shape of the second structure 1005 is positioned relatively non-uniformly to the lines of the first structure 1000. The symmetry is checked with respect to the point of symmetry or axis of symmetry of the pupil image 1030, ie in this case axis 1032, which axis is now denoted by axis 1034.

The physical instance of the unit cell of FIG. 10B can be illuminated with radiation, for example using the metrology device of FIG. 7. The pupil image of the redirected radiation can be recorded, for example, by the detector 190. An example of such a pupil image is shown as a pupil image 1060. The pupil image 1060 is an image of substantially intensity. Although the pupil image 1060 has a diamond shape, it need not be this shape; It can be a circular shape or any other shape. Moreover, the pupil image 1060 has substantially the same axis or coordinate position as the pupil image 1030. That is, in this embodiment, the axis of symmetry 1010 of the unit cell of FIG. 10A and the same axis of the unit cell of FIG. 10B are aligned with the axis of symmetry 1032 of the pupil images 1030 and 1060.

With respect to the pupil image 1060 corresponding to the geometrically symmetric unit cells of the first and second structures 1000 and 1005, the intensity distribution appears to be almost essentially symmetric within the pupil image. However, an asymmetric intensity distribution part exists in the pupil image. This part of the asymmetric intensity distribution is due to the asymmetry in the unit cell. Moreover, the asymmetric intensity distribution is much smaller in size than the symmetric intensity distribution portion in the pupil image.

Therefore, in one embodiment, the symmetrical intensity distribution portion may be removed from the pupil image 1060 in order to more effectively isolate this asymmetrical intensity distribution portion, resulting in a derived pupil image 1065. Similar to obtaining the derived pupil image 1035, as described above, a particular pupil image pixel (e.g., a pixel) is of a pupil image pixel positioned symmetrically from the intensity at that particular pupil image pixel. It is possible to have the symmetrical intensity distribution part removed by subtracting the intensity, and vice versa. Therefore, for example, considering the pupil image 1060, the symmetric intensity distribution part is located symmetrically from the intensity (Ii) at the specific pixel displayed, that is, symmetrically about the axis 1032. It can be removed by subtracting the intensity (Ii') from the pixel to provide Si. This may be repeated for a plurality of pixels of the pupil image, for example all pixels in the pupil image. In FIGS. 10A and 10B, a fully derived pupil image of Si is shown, for example. As can be appreciated, half of the derived pupil image of Fig. 10A or 10B is equal to the other half. Therefore, in one embodiment, the value obtained from only half of the pupil image can be used for the further processing discussed herein, and the image pupil thus derived used in the further processing is in this specification only the Si value for the pupil. It can be half.

As observed in the derived pupil image 1065, the intensity distribution measured using a physical instance of an asymmetric unit cell is not symmetric. As observed in regions 1075 and 1080, there is an observable asymmetric intensity distribution portion if the symmetric intensity distribution portion is removed. As mentioned above, a fully derived pupil image 1065 is shown, and thus portions of the asymmetric intensity distribution are displayed in both two quadrants (even if they are the same in terms of size and distribution within each two quadrant).

Thus, the asymmetry in the geometric domain corresponds to the asymmetry in the pupil. Therefore, in one embodiment, it is possible to retain or handle the geometric symmetry inherent in its own physical instance of the unit cell, causing the geometric symmetry of the physical instance of the unit cell to change (e.g., causing an asymmetry or A method is provided for determining a parameter corresponding to a periodic periodic configuration change, causing a symmetric unit cell to be symmetric. In particular, in one embodiment, overlay-induced asymmetry (or lack of symmetry) within the pupil as measured by the metrology device may be utilized to determine the overlay. That is, pupil asymmetry is used to measure the overlay within the physical instance of the unit cell and thus within the target.

In order to consider how to determine a parameter corresponding to a change in a physical configuration that causes geometric asymmetry in a unit cell, the intensity of a pixel in a pupil image may be considered for a physical characteristic of a target that affects the pixel. To do this, an overlay example will be considered, but the techniques and principles respond to changes in the physical composition that cause geometric asymmetry within the unit cell (e.g., asymmetric sidewall angle, asymmetric bottom wall tilt, ellipticity in the contact hole, etc.). It can be extended to other parameters as well.

,

는 유닛 셀의 상이한 물리적 특성에 기인하는 세기 성분들의 조합으로서 해석적으로 평가될 수 있다. 특히, 대칭적 유닛 셀로부터 비대칭 유닛 셀이 되는 물리적 구성 변화가, 어떠한 방식으로 세기 분포가 특히 퓨필 이미지 내에서 변하는지를 결정하도록 평가될 수 있다.Referring back to the unit cell of FIGS. 10A and 10B, the intensity of the pixel in the pupil image 1060

,

Can be evaluated analytically as a combination of intensity components due to different physical properties of the unit cell. In particular, a change in the physical configuration from a symmetric unit cell to an asymmetric unit cell can be evaluated to determine how the intensity distribution changes, especially within the pupil image.

라고 지정된다. 하지만, 중요하게도, 이러한 높이 변화는 유닛 셀의 물리적 인스턴스에 걸쳐서는 개괄적으로 균일할 것이다. 즉,

는 대칭축 또는 대칭점의 일측에서 대칭축 또는 대칭점의 다른 측에서와 동일하게 변화된 유닛 셀의 물리적 구성을 초래할 것이다. 이와 유사하게, 다른 물리적 구성 변화, 예컨대 CD, 측벽 각도 등의 변화도 유닛 셀의 물리적 인스턴스에 걸쳐서 개괄적으로 균일할 것이고, 따라서 대칭점의 일측에서 대칭축 또는 대칭점의 다른 측에서와 동일하게 변화된, 유닛 셀의 물리적 구성을 초래할 것이다. 그러므로, 편의상,

만이 고려될 것이지만, 이것은 유닛 셀에 걸쳐서 균일한 다수의 다른 물리적 구성 변화들을 대표한다.Therefore, in a very simple example to illustrate this principle, several changes in the physical configuration of the unit cell profile can be evaluated (of course more or other different physical configuration changes may occur). One of the physical configuration changes to be considered is the height change of the structure 1000 in the Z direction, which is

Is designated as However, importantly, this change in height will be generally uniform across the physical instances of the unit cell. In other words,

Will result in the physical configuration of the unit cell being changed the same as on the axis of symmetry or on the other side of the symmetry axis or on the other side of the symmetry axis. Similarly, changes in other physical configurations, such as CD, sidewall angle, etc., will be generally uniform across the physical instance of the unit cell, thus changing the same as the axis of symmetry on one side of the point of symmetry or the other side of the point of symmetry. Will result in the physical composition of. Therefore, for convenience,

While only will be considered, this represents a number of different physical configuration variations that are uniform across the unit cell.

라고 지칭될 것이다. 물론, 오버레이는 다른 방향 또는 추가적 방향에서 고려될 수 있다. 중요하게도,

는 대칭축 또는 대칭점의 일측에서 대칭축 또는 대칭점의 다른 측과 다른 유닛 셀의 물리적 구성을 초래할 것이다; 대칭 픽셀들의 각각의 쌍은 오버레이에 대한 정보를 가진다. 중요하게도, 거의 모든 타겟 프로파일 파라미터(CD, 높이 등)에 변화가 생기면 퓨필 내에 대칭적 변화를 유도하는 반면에(따라서 대칭적 파라미터라고 간주될 수 있음), 오버레이에 변화가 생기면 측정된 퓨필에 비대칭 변화가 초래된다. 따라서, 오버레이 변화는 비대칭 퓨필 응답을 제공한다. 더 나아가, 전부는 아니더라도 거의 모든 다른 유닛 셀 프로파일 파라미터들은 유닛 셀 또는 퓨필 응답에 비대칭이 나타나게 하지 않는다. 그러나, 이들은 측정된 오버레이 값에 대해 영향을 줄 수 있다. 후술되는 바와 같이, 다른 유닛 셀 프로파일 파라미터는 일차 차수에게는 아무런 영향도 주지 않을 수 있다. 일 실시예에서, 이차 이상의 차수에게는, 다른 유닛 셀 프로파일 파라미터가 오버레이 값을 결정하는 데에 영향을 준다. 그러므로, 더 상세히 후술되는 바와 같이, 퓨필 비대칭을 측정함으로써 오버레이가 결정될 수 있다.Another of the changes in the physical configuration of the unit cell of interest is the relative shift between the structure 1000 and the structure 1005, that is, the change in the overlay 1040. These overlay shifts

Will be referred to as. Of course, overlays can be considered in other or additional directions. Importantly,

Will result in the physical configuration of the unit cell different from the axis of symmetry or the other side of the point of symmetry on one side of the axis of symmetry or point of symmetry; Each pair of symmetric pixels has information about the overlay. Importantly, changes in almost all of the target profile parameters (CD, height, etc.) induce a symmetrical change within the pupil (and therefore can be considered a symmetrical parameter), whereas changes in the overlay will result in asymmetrical changes to the measured pupil. Change is brought about. Thus, the overlay change provides an asymmetric pupil response. Furthermore, almost all, if not all, of the other unit cell profile parameters do not cause asymmetry to appear in the unit cell or pupil response. However, they can affect the measured overlay value. As will be described later, other unit cell profile parameters may have no effect on the first order. In one embodiment, for orders greater than or equal to the second order, other unit cell profile parameters influence determining the overlay value. Therefore, as described in more detail below, the overlay can be determined by measuring the pupil asymmetry.

는 다음과 같이 규정될 수 있다:Specifically, in order to evaluate how the overlay can be determined from the measured pupil asymmetry, the intensity of the pixel i in the pupil image 1060

Can be defined as:

는 조명 방사선에 기인하는 기저 세기이고, a, e, f 및 g는 계수들이다. 그러므로, 이와 유사하게, 퓨필 이미지(1060)의 상보적 대칭 픽셀의 세기

는 다음과 같이 규정될 수 있다:From here

Is the baseline intensity due to the illumination radiation, and a, e, f and g are the coefficients. Therefore, similarly, the intensity of the complementary symmetric pixels of the pupil image 1060

Can be defined as:

에 특유하며 퓨필 이미지(1060) 내의 픽셀의 세기

에 대한 계수 a, b, c, d, e 및 f에 비견된다.Where the coefficients a', b', c', d', e'and f'are the intensity of complementary symmetric pixels

And the intensity of the pixels in the pupil image 1060

It is compared to the coefficients a, b, c, d, e and f for.

가 다음과 같이 평가될 수 있다:Then, the difference in intensity between symmetric pixels in the pupil image 1060

Can be evaluated as follows:

는 수학식 3 에서 볼 수 있듯이 없어진다는 것이 발견되었다. 더 나아가, 예를 들어 대칭성 때문에, 오버레이의 짝수 거듭제곱을 가지는 항들도 대칭적으로 위치된 픽셀들에 대해서 동일하다는 것이 발견되었고, 따라서

과 같은 이러한 항들도 없어진다. 그러면, 대칭적 파라미터를 가지는 오버레이의 조합을 포함하는 항과 홀수 거듭제곱(예를 들어, 1, 3, 5, 7 거듭제곱 등)으로 오버레이만을 가지는 항들만 남는다.For example, because of symmetry, all terms that can only hold symmetric parameters, e.g.

Was found to disappear as can be seen in Equation 3. Furthermore, it has been found that terms with even powers of the overlay are the same for symmetrically positioned pixels, for example because of symmetry, and thus

These terms such as Then, only terms including a combination of overlays having symmetric parameters and terms having only overlays with odd powers (eg, powers of 1, 3, 5, 7, etc.) remain.

는 주로

에 의존한다는 것이 발견되었다. 즉, 세기의 차분

는 대부분 오버레이에 선형적으로 의존하고, 또는 더 중요하게도, 오버레이는 대부분 세기, 구체적으로는 세기의 차분

에 선형으로 의존한다. 따라서, 픽셀의 세기들을 조합하면 적절한 변환 인자와 선형 조합될 경우 오버레이의 양호한 추정값을 제공할 수 있다.In Equation 3 above, the intensity difference

Is mainly

Was found to depend on. That is, the difference in the century

Is mostly linearly dependent on the overlay, or more importantly, the overlay mostly depends on the intensity, specifically the difference in intensity.

Linearly depends on Thus, combining the intensities of the pixels can provide a good estimate of the overlay when linearly combined with an appropriate transform factor.

Therefore, in one embodiment, it has been found that the overlay can be determined from a combination of intensities of a properly weighted pixel (the weight itself serves as a transform factor from intensity to overlay or may be combined with an intensity-overlay transform factor). Became. In one embodiment, the overlay signal may be described as follows:

는 신호 성분 Si의 각각에 대한 각각의 가중치이다(가중치는 신호 성분과 오버레이 사이의 변환 인자로서의 역할을 한다; 위에서 언급된 바와 같이, 그 대신에, 변환 인자는 신호 성분을 오버레이로 변환시키는 작용을 하지 않는 가중치와 조합되어 사용될 수 있음). 일 실시예에서, 가중치

는 그 크기가 오버레이에 관련된 벡터이다. 위에서 언급된 바와 같이, 신호 성분 Si는 측정된 퓨필의 절반에 대해서 결정될 수 있다. 일 실시예에서, 만일 신호 성분 Si가 대칭 픽셀(N)의 모든 쌍(N/2)에 대해서 실질적으로 동일한 크기를 가지고 있으면, 신호 성분 Si는 다음 수학식에 따라 평균화되고 신호 성분 Si 전부로부터 오버레이까지의 변환 인자 C와 결합되어 총 오버레이를 제공한다:

. 그러므로, 일 실시예에서, 가중치는 두 가지 역할을 가질 수 있다 - 하나는 픽셀들의 쌍마다 그 오버레이의 측정에 대한 트러스트(trust)로서의 역할이고, 다른 역할은 신호 성분의 광학 특성(예를 들어, 세기 레벨, 예를 들어 그레이 레벨)의 값을 오버레이 값(예를 들어 나노미터 단위로) 변환하는 것이다. 위에서 논의된 바와 같이, 제 2 역할은 변환 인자에 맡겨질 수 있다.Here, the overlay signal M is a weighted combination of signal components Si in the measured pupil,

Is the respective weight for each of the signal components Si (the weight serves as a conversion factor between the signal component and the overlay; as mentioned above, instead, the conversion factor serves to convert the signal component into an overlay. Can be used in combination with weights that do not). In one embodiment, the weight

Is a vector whose size is relative to the overlay. As mentioned above, the signal component Si can be determined for half of the measured pupil. In one embodiment, if the signal component Si has substantially the same size for all pairs (N/2) of symmetric pixels (N), the signal component Si is averaged according to the following equation and is overlaid from all of the signal components Si. Combined with a conversion factor of C to give the total overlay:

. Therefore, in one embodiment, the weight can have two roles-one as a trust for the measurement of its overlay per pair of pixels, and the other role is the optical properties of the signal component (e.g., It converts the value of the intensity level (eg, gray level) to the overlay value (eg, in nanometers). As discussed above, the second role can be left to the conversion factor.

However, for example, if the signal component Si does not have substantially the same size for all pairs of symmetric pixels, a low signal-to-noise ratio (poor precision) will be obtained if all pixels in the measured pupil are weighted equally. I can. Therefore, it is desirable to weight those pixels that are sensitive to the overlay to contribute more to the calculation of the overlay. Therefore, in one embodiment, overlay-sensitive pixels have a different (eg, higher) weight than those pixels that have low sensitivity to the overlay (substantially inactive pixels). As mentioned above, the pixels within regions 1075 and 1080 of the derived pupil 1065 have a relatively higher sensitivity to the overlay, while intensities that are relatively low or zero for pixels within regions 1075 and 1080. The remaining pixels in the derived pupil 1065, having a, have low sensitivity to the overlay (and thus should be weighted to contribute less to the overlay decision).

항에 대해서 효과적으로 결정된다. 일 실시예에서, 가중치는

항 및

(및 통상적으로 다른 파라미터, 예컨대 CD, 측벽 각도 등에 대한 다른 비견한 항)에 대해서 결정되도록 확장될 수 있다. 그러나, 이러한 계산은 수학식 3 의

항에 대해서만 효과적으로 가중치를 결정하는 것에 비하여 더 복잡할 수 있다. 더욱이, 비선형 프로세스(대칭적 파라미터에 대한)에 대한 견실성과 오버레이를 결정하는 정밀도(즉, 결정된 값이 동일한 실제 오버레이의 각각의 결정에 대해서 얼마나 가까운지에 대한 정밀도) 사이에는 트레이드오프가 존재한다. 그러므로, 이러한 계산을 사용하여 견실성을 향상시키려면 정밀도가 희생될 수 있다. 따라서, 정밀도를 향상시키고(예를 들어, 선형 항의 영향을 최대화하고 비선형 항을 억제함), 견실성을 향상시키기 위하여(예를 들어, 비선형 항을 최대화함), 또는 이들 사이에 균형을 찾기 위하여 최적화가 수행될 수 있다. 하지만, 어떠한 경우에서도, 연관된 가중치와 선형으로 조합된 세기의 조합을 사용하면 오버레이를 빨리 결정할 수 있는데, 그 이유는 단순히 퓨필 획득 및 수학식 4 의 간단한 계산만이 필요하기 때문이다.In one embodiment, the weight of Equation 3

Is effectively determined for terms. In one embodiment, the weight is

Term and

(And typically other comparable terms for other parameters such as CD, sidewall angle, etc.) can be extended to determine. However, this calculation is

It can be more complex than effectively determining the weights for terms only. Moreover, there is a tradeoff between the robustness for a nonlinear process (for symmetrical parameters) and the precision of determining the overlay (i.e., how close the determined value is for each decision of the same actual overlay). Therefore, precision can be sacrificed to improve robustness using these calculations. Thus, to improve precision (e.g. to maximize the effect of linear terms and suppress nonlinear terms), to improve robustness (e.g. to maximize nonlinear terms), or to find a balance between them. Optimization can be performed. However, in any case, if the combination of the associated weight and the linearly combined intensity is used, the overlay can be determined quickly, because only pupil acquisition and simple calculation of Equation 4 are required.

및/또는 다른 더 높은 차수 항을 가지는 수학식 3 을 풀도록 비선형 솔루션 기법이 채택될 수 있다. 이해될 수 있는 것처럼, 비선형 솔루션 기법은 단순히 측정된 퓨필 내의 각각의 신호 성분 Si를 각각의 신호 성분 Si에 대한 각각의 가중치

로 승산하고 이들을 모두 합산하는 것보다 더 복잡할 수 있다. 더욱이, 비선형 프로세스에 대한 견실성과 오버레이를 결정하는 정밀도(즉, 결정된 값이 동일한 실제 오버레이의 각각의 결정에 대해서 얼마나 가까운지에 대한 정밀도) 사이에도 역시 트레이드오프가 존재한다. 그러므로, 이러한 계산을 사용하여 견실성을 향상시키려면 정밀도가 희생될 수 있다. 따라서, 정밀도를 향상시키고 및/또는 견실성을 향상시키기 위해서 최적화가 수행될 수 있다.In one embodiment, when higher order terms become larger,

And/or other higher-order terms, a nonlinear solution technique may be employed to solve equation (3). As can be understood, the nonlinear solution technique simply adds each signal component Si in the measured pupil to each weight for each signal component Si.

It can be more complicated than multiplying by and summing them all together. Moreover, there is also a tradeoff between the robustness for a nonlinear process and the precision that determines the overlay (ie, how close the determined value is for each decision of the same actual overlay). Therefore, precision can be sacrificed to improve robustness using these calculations. Accordingly, optimization can be performed to improve precision and/or improve robustness.

Therefore, by implementing the asymmetric intensity distribution from the geometric asymmetry of the unit cell caused by the overlay, the error of the overlay can be determined through an analysis emphasizing this asymmetric intensity distribution. Accordingly, a technique for determining the overlay from the asymmetric intensity distribution resulting from a change in the physical configuration of the target associated with the overlay will now be discussed.

Referring to Fig. 11, a method of determining weights is schematically depicted. In order to determine the weights, the reconstruction technique described above in FIG. 9 will be advantageously used. That is, in one embodiment, CD reconstruction is used to isolate the overlay signal from the pupil image of the physical instance of the asymmetric unit cell.

The method of FIG. 11 involves two processes. The first process 1100 uses a reconstruction technique for the CD and/or one or more other profile parameters of the target, the nominal profile of the target exposed on the substrate as part of the patterning process (and thus one or more of the unit cells in the target). It entails deriving the nominal profile of the physical instance). If there is a nominal profile of the target, the basic engine of the reconstruction technique is used in process 1110 to derive the weights. Then, the weight can be used to derive an overlay from the measured pupil, as will be described further with respect to FIG. 12.

Therefore, in process 1100, measurements 1130 of a substrate having one or more physical instances of a unit cell of interest provided on the substrate as a target are obtained. In one embodiment, the measurements relate to the target after etching. In one embodiment, the measurements relate to the target after development and before etching. In one embodiment, the target is a device structure. In one embodiment, the measurement may have been or may have been performed using a measurement device such as the measurement device of FIG. 7. For example, the target may comprise a physical instance of the unit cell of FIG. 10A or 10B, for example a single instance as shown in FIG. 10C or a plurality of adjacent instances. In one embodiment, measurements of a plurality of targets (and thus measurements of physical instances of a plurality of unit cells) are obtained. In one embodiment, the measurements are for targets distributed across the substrate. In one embodiment, a plurality of substrates are measured, each having one or more targets (each having one or more physical instances of a unit cell). Therefore, in one embodiment, a radiation distribution 108 is obtained for each measured target.

The reconfiguration process at 1100, e.g., the reconfiguration process described in connection with FIG. 9, is then used to derive a nominal profile of the physical instance of the unit cell compared to the profile 206 of FIG. 9. The reconfiguration process initiates and facilitates the reconfiguration process by obtaining the expected profile 1120 of the physical instance of the unit cell. In one embodiment, the derived nominal profile is obtained from an average of the profiles of targets across one or more substrates. For example, the radiation distribution 108 for each target is processed to derive a specific profile of that instance of the target, and the profiles of a plurality of instances of the target are then averaged together to derive a nominal profile. In one embodiment, the nominal profile includes at least the geometrical profile of the target. In one embodiment, the geometrical profile is a 3-D profile. In one embodiment, the nominal profile includes information related to one or more material properties of one or more layers constituting a physical target.

Therefore, in one embodiment, the nominal profile is based on the values of various parameters of the profile of the target (and thus the unit cell), obtained by measuring multiple instances of the target across the substrate or, optionally, measuring on more than one substrate. It can be regarded as the center of gravity. However, in one embodiment, the nominal profile may have a different shape and may be more unique. For example, a nominal profile can be defined for one or more specific instances of a target (eg, by using values obtained from the same target location(s) from multiple substrates). As another example, a nominal profile can be defined for a particular substrate (eg, by using only values from that substrate). In one embodiment, the nominal profile may be tuned for a specific target and/or substrate as part of the process of FIG. 12. For example, a target and/or substrate is measured as part of the process of FIG. 12, and a reconstruction technique can be used with the measured data to fine-tune the nominal profile for that target and/or substrate, which can then be fine-tuned. A tuned nominal profile can be used herein as a nominal profile to determine the weights, and these weights can now be used with the same measured data to provide one or more overlay values.

The reconstruction nominal profile 1140 is then provided to the process 1110. Thus, in one embodiment, the process 1110 uses the derived nominal profile of the target, e.g., the geometric post-etch profile of the device's unit cells, derived from measured data. In one embodiment, the nominal profile is parameterized according to the measured unit cell

It may be in the form of a parameterized model, such as model 206. Thus, in one embodiment, process 1110 uses a derived profile model of a unit cell, eg, a model of a geometrical post-etch profile of a physical instance of a unit cell of a device derived from measured data.

The basic engine of the reconstruction technique described herein is used in process 1110 with the derived profile or the derived profile model to derive the weights. In one embodiment, a derived profile model or a derived profile model that has been derived from a derived profile is used to determine the pupil pixels that are insensitive to the overlay in the unit cell. In particular, in one embodiment, the sensitivity of the pupil response to the overlay is determined using a simulation (eg, a Maxwell solver) to determine the change in the pupil response to the induced change of the overlay to the nominal profile.

This can be achieved by making the derived profile model change and all other parameters/variables of the derived profile model unchanged so that a certain amount (eg 1 nm) of the overlay change is derived in the model. In practice, this causes the symmetrical unit cell to become asymmetric or to cause the already asymmetric unit cell to change the symmetry (make it more asymmetric or change from an asymmetric situation to symmetric).

Then, the pupil to be expected in the measurement device (e.g., measurement device for radiation having a specific measurement beam wavelength, measurement beam polarization, measurement beam intensity, etc.) is derived based on the derived profile model with the induced overlay change. Can be (e.g., using a Maxwell solver, library search, or other reconstruction technique). If the physical instance of the unit cell is smaller than the beam spot, the reconstruction can be treated as if the beam spot is filled with the physical instance of the unit cell. In one embodiment, the derived pupil may be a simulated pupil image 1060 and/or a derived pupil image 1065 based on the simulated pupil image.

Then, the derived pupil can be used to determine the sensitivity to an overlay change in intensity in a plurality of pupil pixels, for example, by comparison with the derived pupil for the unit cell without the induced overlay (e.g. For example, the derived pupil for a unit cell without a derived overlay may be a simulated pupil image 1030 and/or a derived pupil image 1035 based on the simulated pupil image). In one embodiment, this sensitivity is the basis of the weight.

항에 대해서 효과적으로 결정된다. 야코비안 행렬 또는 야코비안 행렬의 무어-펜로즈 의사 역행렬으로부터 유도되는 가중치는, 상대적으로 적은(예를 들어, ±3 nm 내 또는 ±4 nm 내 또는 ±5 nm 내) 오버레이 변동에 대해서 잘 적용되는 것으로 보인다.In one embodiment, pixels of the pupil (thus pixel intensity, signal component Si, etc.) may be represented as vectors. In one embodiment, weights can now be derived from the Jacobian matrix generated during modeling. In an embodiment, the weight may be derived from a Moore-Penrose pseudo inverse of a Jacobian matrix generated during modeling. Therefore, the weight of Equation 3

Is effectively determined for terms. Weights derived from the Jacobian matrix or the Moore-Penrose pseudo-inverse of the Jacobian matrix are well applied for relatively small (e.g., within ±3 nm or within ±4 nm or within ±5 nm) overlay variations. see.

항 및

(및 통상적으로 다른 파라미터, 예컨대 CD, 측벽 각도 등에 대한 다른 비견한 항)에 대해서 결정되도록 확장될 수 있다. 이러한 경우에, 가중치는 야코비안 행렬에 추가하여, 모델링 중에 생성된 헤시안(Hessian) 행렬이거나 그로부터 유도될 수 있다. 헤시안은 오버레이에 대한 응답이 특정량의 다른 (대칭적) 파라미터(예컨대 CD)의 변화에 기인하여 어떻게 변하는지를 보여준다. 그러므로, 이러한 파라미터 모두에 대하여 헤시안 내에는 열이 존재한다. 일 실시예에서, (더) 견실해지기 위하여, 유닛 셀이 민감성을 가지는 열(파라미터)에 대해서 더 많이 직교하게 되도록 가중치가 변경될 수 있다. 더 많이 직교하기 위하여, 하나 이상의 감도 높은 열이 야코비안에 연쇄(concatenate)될 수 있고, 그러면 무어-펜로즈 의사 역행렬이 헤시안으로부터 나온 하나 이상의 열이 연쇄된 이러한 야코비안으로부터 계산될 수 있다. 이러한 계산으로부터 가중치가 나온다. 그러나, 이러한 계산은 더 복잡할 수 있고, 따라서 오버레이 값이 실제로, , 야코비안 행렬(의 무어-펜로즈 의사 역행렬)로부터 유도된 가중치가 양호한 결과를 나타내는 오버레이 변동 범위를 초과할 것으로 기대되는 상황에 대해서 적합할 수 있다.In one embodiment, the weight is

Term and

(And typically other comparable terms for other parameters such as CD, sidewall angle, etc.) can be extended to determine. In this case, the weight may be or may be derived from a Hessian matrix generated during modeling, in addition to the Jacobian matrix. Hessian shows how the response to the overlay changes due to a change in a certain amount of other (symmetric) parameters (eg CD). Therefore, there is heat in Hessian for all of these parameters. In one embodiment, in order to be (more) robust, the weight may be changed so that the unit cell is more orthogonal to the sensitive column (parameter). To be more orthogonal, one or more sensitive columns can be concatenated into Jacobians, and then the Moore-Penrose pseudo-inverse matrix can be computed from these Jacobians in which one or more columns from Hessian are concatenated. Weights come from these calculations. However, these calculations can be more complex, so for situations where the overlay values are actually expected to exceed the range of overlay fluctuations, where the weights derived from the Jacobian matrix (the Moore-Penrose pseudo-inverse matrix) are expected to exceed the range of overlay fluctuations that give good results. May be suitable.

In one embodiment, the weight may be extended to be determined for other terms in Equation 3. In that case, the weights can be derived from or are cubic derivatives generated during modeling, in addition to the Jacobian matrix.

의 효과를 억제하기 위해서 사전에 선택되었을 수 있지만, 미세 튜닝이 해당 타겟 및/또는 기판에 대해서

를 식별하고 업데이트하면,

의 효과는 억제될 필요가 없을 수도 있다. 따라서, 견실성보다 정밀도를 우선시하는 가중치가 선택될 수 있다.As mentioned above, the nominal profile can be a fine tuned nominal profile per target or substrate. For example, if a particular target or substrate is measured as part of the process of FIG. 12, a reconstruction technique may be used with the measured data to fine tune the nominal profile for that target or substrate. Now, depending on fine tuning, the weights can be (re-)determined and/or a choice can be made between the types of weights that are made (eg Jacobian or a combination of Jacobian and Hessian). For example, weights based on nominal profiles that were not fine tuned

May have been pre-selected to suppress the effect of the target, but fine tuning is required for that target and/or substrate.

Identify and update,

May not need to be suppressed. Thus, a weight that prioritizes precision over robustness can be selected.

의 콜렉션(예를 들어, 벡터)이 출력될 수 있다. 가중치

는 그 자체로 세기-오버레이의 변환 인자로서의 역할을 할 수 있고, 또는 가중치는 세기-오버레이의 변환인자와 조합될 수 있다(이러한 변환 인자는 동일한 모델링의 일부로서 유도될 수 있음). 퓨필 이미지(1065)로부터 이해될 수 있는 것처럼, 지역(1075 및 1080) 내의 픽셀은 지역(1075 및 1080) 밖의 픽셀들보다 오버레이에 대해 상대적으로 높은 감도를 가지고, 따라서 그들의 가중치는 지역(1075 및 1080) 밖의 픽셀(이러한 픽셀은 오버레이에 대해 상대적으로 낮은 감도를 가짐)의 가중치와 크게 다를 것이다(예를 들어, 더 높음). 그러므로, 가중치는 유닛 셀의 하나 이상의 물리적 인스턴스를 가지는 타겟의 측정된 세기 값과 조합(예컨대, 수학식 4 에 따라서)되고, 오버레이 신호가 특정 타겟(예컨대 유닛 셀의 물리적 인스턴스를 가지는 디바이스 패턴)에 대해서 획득될 수 있다.Therefore, from process 1110, the weight

A collection (for example, a vector) of can be output. weight

May itself serve as a transform factor of the intensity-overlay, or the weight may be combined with the transform factor of the intensity-overlay (this transform factor can be derived as part of the same modeling). As can be understood from pupil image 1065, pixels within regions 1075 and 1080 have a relatively higher sensitivity to overlay than pixels outside regions 1075 and 1080, so their weights are based on regions 1075 and 1080. ) Will differ significantly from the weight of the pixels outside (such pixels have a relatively low sensitivity to the overlay) (e.g. higher). Therefore, the weight is combined with the measured intensity value of the target having one or more physical instances of the unit cell (e.g., according to Equation 4), and the overlay signal is applied to a specific target (e.g., a device pattern having a physical instance of the unit cell). Can be obtained for.

Furthermore, one or more measurement parameters may be determined to form a measurement strategy for use in obtaining the measured intensity value of the target. One or more measurement parameters can affect the overlay sensitivity of the pixel. For example, the overlay sensitivity varies over different measurement beam wavelengths. Therefore, in one embodiment, several optical property readings read by the detector sensor of one or more measurement parameters (e.g. wavelength, polarization, dose, specific illumination of the target, these readings are typically averaged and compared to the measurements of the target). (Providing an averaged optical property value for)) may be modified as part of the modeling process 1110. For example, if one or more measurement parameters are investigated for a particular induced overlay change, for example, if the weight is for one value of one or more parameters, the acquired overlay and weights are for different values of one or more parameters. The error residuals between the overlays obtained in the case of one can be reduced to a minimum value or below a certain threshold. Therefore, the values of one or more measurement parameters can now be obtained with improved corresponding precision.

Furthermore, the robustness to process variation varies across different values of one or more measurement parameters. In particular, for example the robustness to process variations varies across different values of the measurement beam wavelength and/or measurement polarization. Thus, in one embodiment, the weighting scheme must address at least the dominant contributing factor to the lack of robustness against process variation. Therefore, in addition to or alternatively to determining the value of one or more measurement parameters for improved precision, one or more measurement parameters are different specifically derived overlay change values (and/or of one or more other parameters of the derived profile model). Values of one or more measurement parameters can be obtained that are inspected for specific induced changes, such as changes in CD, sidewall angle, etc., resulting in results using weights that improve robustness against process variations. For example, for different amounts of induced overlay change, various values of one or more measurement parameters may be evaluated so that the minimum variation (or variation below a threshold) of the determined overlay using the weights associated with the values of the one or more measurement parameters. It is possible to determine the value of one or more measurement parameters that result. Of course, a balance can be used to select the value of one or more measurement parameters between precision and improved robustness. For example, the value of one or more measurement parameters determined for precision (e.g., the weight applied to a performance metric measuring precision) and the value of one or more measurement parameters determined for improved robustness (e.g., measuring robustness). The weight applied to the performance metric) may be applied, and then a combination such as the largest and highest ranking may be selected. Of course, a plurality of values of one or more measurement parameters may be determined such that there are in fact a plurality of different measurement strategies in the overall measurement strategy. A plurality of values may be ranked according to one or more performance metrics. Thus, optionally, some measurement strategy may be output from process 1110 for use in obtaining the measured intensity value of a target having one or more physical instances of a unit cell.

Furthermore, one or more non-overlay parameters, such as CD, sidewall angle, etc., may affect the weights used to map the intensity signal to the overlay. As mentioned above, an exemplary way to determine weights in this context is to use a Hessian matrix and/or a cubic derivative. Therefore, in one embodiment, various possible weighting schemes may take into account one or more non-overlay parameters in order to maintain a good overlay value. In one embodiment, overlay informative overlay pixels and their weights can be optimized for overlay decision precision. This may require good model quality, ie good estimation of non-overlay parameters. In one embodiment, the overlay-information pixels and their weights may be optimized to increase robustness to process variations in non-overlay parameters, for example. This can sacrifice precision.

In one embodiment, the estimation of one or more non-overlay parameters is made, for example, using the reconstruction technique described in connection with FIG. 9, and can be fed-forward to tune the derived profile or the derived profile model. . For example, CD reconstruction estimates the CD for a specific combination of CD and/or patterning process settings (e.g., exposure dose, exposure focus, etc.) of a target at a specific location on the substrate, and uses that CD estimate. Thus, the derived profile or the CD parameter of the derived profile model can be tuned. In one embodiment, an iterative reconstruction of the correct derived profile or derived profile model parameters may be performed.

Referring to FIG. 12, a method of determining an overlay value for a target having one or more physical instances of a unit cell that may be geometrically symmetric is illustrated. This method involves two processes 1200 and 1210. Process 1200 involves obtaining a measure of a target having one or more physical instances of a unit cell. Process 1210 involves determining an overlay value for the measured target based on the measurement of the target, from process 1200.

Process 1200 takes as input a target to be measured 1220 comprising one or more physical instances of a unit cell as described herein, which may be geometrically symmetric. In one embodiment, a substrate with one or more instances of a target is provided with a metrology device, such as the metrology device of FIG. 7.

Alternatively, process 1200 obtains as input a specific measurement strategy 1230 defined for that target. In one embodiment, the measurement strategy is one or more measurement parameters, such as measurement beam wavelength, measurement beam polarization, measurement beam dose, and/or a number of optical properties read by the detector sensor of the metrology device of a particular illumination of the target. One or more values selected from among the values can be defined. In one embodiment, the measurement strategy may include a plurality of measurement strategies that specify values of one or more measurement parameters. Measurement strategies can be used to measure targets.

The process 1200 then measures the target using a metrology device according to an optional measurement strategy. In one embodiment, the metrology device obtains a pupil representation of the redirected radiation. In one embodiment, the metrology device displays a pupil representation, such as a pupil image 1030 (e.g., if the target has no error in the overlay) or a pupil image 1060 (e.g., if the target has an error in the overlay). Can be generated. Thus, in one embodiment, the process 1200 outputs optical information 1240 related to the redirected radiation from the target, such as a pupil representation of the radiation.

Then, the process 1210 receives the optical information 1240 and processes the optical information to determine an overlay value 1260 for the target. In one embodiment, process 1210 receives as input the weights 1250 determined in the method of FIG. Is combined with

In one embodiment, process 1210 (or process 1200) may process optical information to derive a raw overlay signal from the optical information. In one embodiment, the raw overlay signal comprises a difference in optical information, i.e., a difference in optical characteristic values between symmetric pixels across an axis of symmetry or a point of symmetry. In one embodiment, a derived pupil image 1035 (for example, if the target does not have an error in the overlay) or a derived pupil image 1065 (for example, if the target has an error in the overlay) may be obtained. have.

를 사용하며 원시 오버레이 신호로부터 얻은 신호 성분 Si의 가중된 조합으로서 계산된다.In one embodiment, the weight and optical information for the radiation redirected by the target (e.g., optical information from process 1200 or a processed version of optical information from process 1200 such as a raw overlay signal) is Combined to determine the overlay value. In one embodiment, the use of a combination of the associated weights and linearly combined redirected measurement beam intensities can be used to quickly determine the overlay. For example, in one embodiment, the overlay value may be derived from Equation 4, where the overlay value M is an individual weight for each of the signal components Si.

And is calculated as a weighted combination of signal components Si obtained from the raw overlay signal.

In one embodiment, the optical information collected from process 1200 may be additionally used to derive one or more target related parameters other than overlay. For example, optical information collected from process 1200 can be used in a reconstruction process to derive any one or more geometric profile parameters of the target, such as CD, sidewall angle, bottom floor tilt, and the like. Therefore, in one embodiment, the same set of optical information collected from the target, such as the target after in-die etching, may be used to determine the CD and/or one or more other geometrical profile parameters of the target (eg device structure).

및

(다시 표시는 대칭 위치를 나타냄)의 경우, 그러한 픽셀에 대한 반사도 R이 다음과 같이 측정될 수 있다:As mentioned above, although emphasis is placed on intensity, in one embodiment the optical property may be reflectivity, the radiation may be polarized, and the measurement may be a cross-polarized measurement. For example, a target exposed with a specific linear polarization can be measured with that polarization or at a different polarization. Therefore, symmetric pixels

And

In the case of (again indicating a symmetrical position), the reflectivity R for such a pixel can be measured as follows:

는 타겟이 s 편광을 사용하여 조명되었을 때에 측정된 s 편광된 방사선의 반사도 R에 대응하고, 반사도

는 타겟이 p 편광을 사용하여 조명되었을 때에 측정된 s 편광된 방사선의 반사도 R에 대응하며, 그 외에도 마찬가지이다. 더욱이, 이러한 측정치는 상이한 파장에서 취해질 수 있다. 그리고, 특정 실시예들에서, 오버레이 변화에 응답하여 자신의 대칭을 바꾸는 대칭적 유닛 셀에 대한 오버레이가 합동체(congruent)

및

로부터 발견되고 결정될 수 있다는 것이 발견되었다.Here, s represents polarized light and p represents polarized light. Therefore, the reflectivity

Corresponds to the reflectivity R of the s polarized radiation measured when the target is illuminated using s polarized light,

Corresponds to the reflectivity R of s-polarized radiation measured when the target is illuminated using p-polarized light, and so on. Moreover, these measurements can be taken at different wavelengths. And, in certain embodiments, the overlay for a symmetric unit cell that changes its symmetry in response to the overlay change is congruent.

And

It has been discovered that can be found and determined from

Furthermore, nonlinearities can arise from overlays and/or other parameters. As discussed above, certain nonlinearities can be resolved by appropriate selection of weights, for example by deriving the weights using a Hessian matrix and/or a cubic derivative. In one embodiment, nonlinearity may be addressed by using a nonlinear solution to derive an overlay from measured optical information of radiation redirected from the target.

In one embodiment, the overlay may be determined using a reconstruction engine as described above used to derive the nominal profile. For example, a model derived from the derived nominal profile and/or a nonlinear solver operating from the derived nominal profile model may be used to derive a simulated version of the expected optical information from the redirected radiation from the target of interest, This can be compared to the measured optical information of the target of interest. As mentioned above, a target of interest can be symmetric and contains one or more physical instances of a unit cell that changes its symmetry when exposed to an overlay. Then, if no agreement is reached within a certain threshold, the geometrical profile parameter (e.g., overlay) is changed, and the simulated version of the optical information can be recalculated and compared to the measured optical information until there is agreement within the threshold. . Similarly, the measured optical information of the target of interest can be compared against a library of optical information expected from the redirected radiation from the target of interest (such a library will typically be derived using a nonlinear solver). Then, if no agreement is reached within a certain threshold, the geometrical profile parameter (e.g., overlay) is changed, and the library is referenced for a simulated version of the optical information compared to the measured optical information until agreement is reached within the threshold. I can.

In one embodiment, using the measured optical information from the target of interest and the reconstruction engine uses the measured optical information, from which the symmetrical distribution of radiation is as described above, e.g., optical properties at each pixel. It has been removed from the value by subtracting the value of the optical property at the point of symmetry or the pixel located symmetrically across the axis of symmetry. Thus, the optical information relates substantially only to the asymmetric distribution of radiation. Similarly, a simulated or library version of optical information relates substantially only to the asymmetric distribution of radiation. Then there will be no need to be calculated or evaluated since a significant portion of the optical information will be erased through differentiation, thus facilitating calculation and/or comparison times.

를 유도할 수 있다. 특히, 수학식 3 의

,

,

등(적용가능한 경우)의 값은 관심 유닛 셀의 유도된 공칭 프로파일 및/또는 유도된 공칭 프로파일 모델을 결정하는 것의 일부로서 결정될 수 있다. 예를 들어, 유도된 공칭 프로파일이 비선형 재구성의 일부로서 결정되면, 유도된 공칭 프로파일에 대응하는(예를 들어, 오버레이의 특정한 변화에 대한 유도된 공칭 프로파일의 섭동(예를 들어,

)에 대응하는) 퓨필에 대한 시뮬레이션된 또는 라이브러리 광학적 정보가 획득될 수 있고, 그러면 a, b, c 등(적용가능한 경우)의 값이 잔차를 최소화하기 위해서, 예를 들어 솔루션들을 통해서 반복하는(예를 들어, 오버레이 내의 하나 이상의 섭동(예를 들어,

)에 응답하여) 비선형 솔버를 이용하여 각각의 픽셀에 대해서 결정될 수 있다. 그 결과는, 적용가능한 경우 퓨필에 대한 a 값(각각의 a 값은 퓨필의 픽셀에 대응함)의 벡터, 퓨필에 대한 b 값(각각의 b 값은 퓨필의 픽셀에 대응함)의 벡터, 퓨필에 대한 c 값(각각의 c 값은 퓨필의 픽셀에 대응함)의 벡터 등이다. 그러면, 이러한 벡터는 관심 유닛 셀을 가지는 타겟의 측정된 퓨필로부터 결정된

값들의 벡터와 조합될 수 있다. 예를 들어 잔차를 최소화하기 위해서 솔루션들을 통해서 반복하는 비선형 솔버는 이러한 입력 벡터를 취하고 오버레이

에 대해서 풀이할 수 있다.In a further embodiment of the nonlinear solution, the expansion of equation 3 is solved with a nonlinear solver

Can induce In particular, in Equation 3

,

,

The value of etc. (if applicable) can be determined as part of determining the derived nominal profile and/or derived nominal profile model of the unit cell of interest. For example, if the derived nominal profile is determined as part of the nonlinear reconstruction, then the perturbation of the induced nominal profile corresponding to the derived nominal profile (e.g., for a specific change in the overlay (e.g.

The simulated or library optical information for the pupil can be obtained, and then the values of a, b, c, etc. (if applicable) iterate through the solutions, e.g., to minimize residuals ( For example, one or more perturbations within the overlay (e.g.,

In response to )) can be determined for each pixel using a nonlinear solver. The result is a vector of a values for the pupil (each a value corresponding to a pixel in the pupil), a vector of b values for the pupil (each b value corresponding to a pixel in the pupil), and a vector for the pupil, if applicable. It is a vector of c values (each value of c corresponds to a pixel in the pupil). Then, this vector is determined from the measured pupil of the target having the unit cell of interest.

Can be combined with a vector of values. For example, a nonlinear solver that iterates through solutions to minimize residuals takes these input vectors and overlays them.

Can be interpreted for.

Although the above discussion has focused on using a model to model the physical profile of a unit cell, in one embodiment the weights can be derived using a data-driven technique that does not require physical profile modeling or It can be derived with complementary data-driven techniques. Therefore, in one embodiment, the data-driven scheme may preferably not require a physical profile model; This limits the sharing of confidential information, for example, because physical profile modeling begins with or determines it with details related to the unit cell (and thus the target), which may be sensitive information if the unit cell is a device pattern structure. It can be useful to do. In one embodiment, the data-driven technique enables relatively fast determination of weights, e.g., as discussed above, so that the measured optical information (e.g., pupil intensity) is converted into a patterning process parameter (e.g. , Overlay). In one embodiment, the data-driven technique allows the patterning process parameters to be determined in a fast stage, as the data-driven technique may require only measured data and associated references, as described below.

Therefore, in one embodiment, the data-driven technique is from one or more substrates having one or more specific set values of a patterning process parameter of interest (e.g., an overlay) and having a physical instance of the unit cell of interest patterned thereon. It involves processing measured data ("get" data). This combination of "set" intentional values of a particular patterning process parameter (eg, an overlay) together with a pattern to produce measured data ("get" data) from that pattern is a "set-get" -get)" process. For example, an overlay of a certain amount of physical instances of a unit cell is created as part of the patterning process, so that a target with a physical instance of the unit cell can, for example, create a pupil image of it (i.e., "get" data). It is measured to obtain. In one embodiment, a plurality of substrates can be patterned and measured in this manner. In one embodiment, a plurality of different setting values of the overlay are created, those different values of the overlay may be for one substrate or may span different substrates. In one embodiment, each substrate will have a plurality of targets measured, for example providing a plurality of pupil images. In one embodiment, the overlay may be created by deriving a magnification change from design magnification between patterning different portions of a physical instance of a unit cell. In one embodiment, the overlay may be created by providing intentional translation from design positioning between patterning different portions of a physical instance of a unit cell. Thus, the result is a deliberately applied overlay in a target induced by a lithographic apparatus for example.

In one embodiment, in general, there are acquired measurement data and associated reference values. Therefore, in one embodiment, if different overlays exist but those overlays are determined by other means (eg, from a scanning electron microscope), an intentional overlay need not be provided. In one embodiment, a critical dimension uniformity substrate with corresponding reference data (eg, data obtained from CD-SEM) may be used as input data. Given the measured data and reference values, the data-driven approach can find the weights such that the inferred overlay value is similar to the reference value, as discussed herein. Therefore, although the discussion of data-driven techniques focuses on the measured optical information and pupil representation at intentionally set overlay values, they can be applied to more general measurement data and associated reference values (measured or intentionally set). .

Furthermore, although the inventive technique relates to a specific overlay (e.g., an overlay in the X-direction), the inventive technique uses the corresponding measurement data and reference values to provide different overlays (e.g., Y-direction). It will be appreciated that it may be repeated for overlays of, overlays between structures in different layers, etc.). Thus, different sets of weights can be determined for different overlays.

Therefore, referring to FIG. 13, a high-level flowchart of an embodiment of a data driving technique is shown. At 1300, calculations are performed to derive the weights as discussed above, transforming the measured optical information (eg, pupil intensity) into patterning process parameters (eg, overlay). In particular, these calculations use multiple inputs. One of the inputs is the set value 1320 of the set-get process for the target having the physical instance of the unit cell of interest. As mentioned above, multiple instances of the target can be measured across one or more substrates, one or more instances of the target having different values of intentionally set values of the patterning process parameters than one or more other instances of the target. . An additional input is the measured optical information 1310 for such instances of the target at different set values. In one embodiment, the optical information 1310 is a plurality of pupil representations, each corresponding to an instance of a target. The inputs 1310 and 1320 are then processed with a data-driven technique to arrive at a weight 1330. Examples of such data-driven techniques are now described below.

를 찾기 위한 데이터-구동 기법의 일 예는 후속하는 목적 함수 또는 메리트 함수를 최소화하여 가중치

에 이르게 하는 것이다:In one embodiment, a vector of weights

An example of a data-driven technique for finding a weight value by minimizing the following objective function or merit function

Is what leads to:

는 측정된 광학 특성(예를 들어, 세기)의 값과 조합되어 패터닝 프로세스 파라미터(예를 들어, 오버레이)를 결정하기 위한 가중치의 벡터이고, 각각의 가중치는 퓨필의 픽셀 값에 대응하며,

는 패터닝 프로세스 파라미터의 특정 설정 값을 얻도록 패터닝된 기판

으로부터 획득된 타겟의 인스턴스의 측정된 퓨필로부터 얻은 측정된 광학 특성의 픽셀 값을 각 열이 보유하는 행렬이고(그러면 이러한 행렬은 열이 퓨필의 픽셀이 되고, 행이 기판 상의 타겟의 하나 이상의 인스턴스가 되도록 전치되고, 행렬의 값은 각각의 픽셀에서의 측정된 광학 특성의 값이다),

는 하나 이상의 기판

상의 타겟의 하나 이상의 인스턴스에 대한 패터닝 프로세스 파라미터의 대응하는 설정 값을 보유하는 벡터이며, 각각의 설정 값은 패터닝 프로세스 파라미터 값에 대응하고,

은 설정 값의 개수만큼의 크기인 단위 벡터이며,

는 각각의 기판에 대한 패터닝 프로세스 파라미터의 설정값과 패터닝 프로세스 파라미터(

)의 추론된 값 사이의 오프셋 차분이며, D는 측정되는 기판의 개수이다. 행렬

는 타겟의 각각의 인스턴스에 대한 상이한 결과들의 조합일 수 있다. 예를 들어, 타겟은 상이한 파장, 상이한 편광 등으로 측정될 수 있다. 그러므로, 이러한 결과는 각각의 열에 연쇄될 수 있어서, 예를 들어 하나의 열은 제 1 파장 및 제 1 편광으로 측정된 타겟의 퓨필의 픽셀에 대한 값들을 가질 수 있고, 이들 뒤에는 제 2 의 다른 파장으로 측정된 타겟의 퓨필의 픽셀에 대한, 열 내의 값들이 후속되거나, 제 2 의 다른 편광으로 측정된 타겟의 퓨필의 픽셀에 대한, 열 내의 값들이 후속될 수 있다(이들 뒤에도 하나 이상의 상이한 편광 및/또는 파장에서의 추가적인 값들이 후속할 수 있다).From here

Is a vector of weights for determining a patterning process parameter (e.g., overlay) in combination with a value of the measured optical characteristic (e.g., intensity), each weight corresponding to a pixel value of the pupil,

Is the patterned substrate to obtain a specific set value of the patterning process parameter

Is a matrix in which each column holds the pixel values of the measured optical properties obtained from the measured pupils of the instances of the target obtained from (therefore, these matrices are the columns being pixels of the pupil, and the rows are the Transposed to be possible, and the value of the matrix is the value of the measured optical properties at each pixel),

Is one or more substrates

Is a vector holding corresponding set values of the patterning process parameters for one or more instances of the target on the image, each set value corresponding to the patterning process parameter value,

Is a unit vector that is as large as the number of set values,

Is the set value of the patterning process parameter for each substrate and the patterning process parameter (

) Is the offset difference between the inferred values, and D is the number of substrates to be measured. procession

May be a combination of different results for each instance of the target. For example, targets can be measured with different wavelengths, different polarizations, and the like. Therefore, these results can be chained to each column, for example one column can have values for the pixels of the target's pupil measured with a first wavelength and a first polarization, followed by a second other wavelength. For a pixel of the pupil of the target measured as, values in the column may be followed, or for a pixel of the pupil of the target measured as a second different polarization, the values in the column may be followed (after one or more different polarizations and /Or additional values in wavelength may follow).

를 찾아내어, 각각의 기판

에 대한 추론 값

가 오프셋

로부터 떨어진 설정-값

와 가능한 한 비슷해 보이게(L2 정규화 놈(norm)의 의미에서) 한다. 이론상, 최적의 가중치 및 오프셋이 행렬 반전에 의하여 계산될 수 있다. 측정된 광학 특성의 픽셀 값들이 하나 이상의 특정 계측 장치로 얻어지기 때문에, 획득된 가중치는 캘리브레이션 데이터에 의해 정규화되어 특정 계측 장치 자체가 결과에 미치는 영향을 감소시킬 수 있다.Hence, as a result, these functions are weight vectors

Find out, each substrate

Inferred value for

Fall offset

Set-value away from

To look as similar as possible (in the sense of the L2 normalization norm). In theory, optimal weights and offsets can be calculated by matrix inversion. Since the pixel values of the measured optical properties are obtained with one or more specific measurement devices, the obtained weights can be normalized by the calibration data to reduce the effect of the specific measurement device itself on the results.

Instead of or in addition to finding the weights using an objective function or a merit function like the data-driven technique as described above, the data-driven technique is a patterning process of interest using a machine learning algorithm such as a neural network, or a nonlinear method. The weight can be determined based on the measured pupil of the target along with the intentionally provided difference in the parameter (eg, overlay).

In one embodiment, after training (ie, training using an objective or merit function or machine learning algorithm), the weights may be checked using other data. Overfit can occur as a result of training; The data-driven approach fits data "just" to a set value. Therefore, cross-authentication is completed. New data with a known set value is used to check the weight. This new data could be a subset of the current substrate. Therefore, in one embodiment, training is performed on a subset of the substrates and authentication is performed on another (disjunct) subset of the substrates.

는, 야코비안(의 무어-펜로즈 의사 역행렬)이 (스케일링된) 가중치 벡터

와 유사하게 되게끔 물리적 기하학적 모델이 튜닝되도록, 물리적 기하학적 모델을 미세 튜닝하기 위해서 사용될 수 있다.14 shows a high level flow of an embodiment of a data-driven technique combined with a physical geometric model. In this embodiment, data-driven techniques such as those described in connection with FIG. 13 may be used to derive the weights, which are physical geometric models (e.g., Jacobian's Moore-Penrose pseudo inverse matrix of physical geometric models )) to be equal to or similar to the weights determined by the data-driven technique (e.g., by value or statistically, etc.), tuning the physical geometric model (e.g., using Hessian to further It is used to obtain a good model nominal value, by changing the model nominal value, etc.). Thus, in one embodiment, the (scaled) weight vector

Is the Jacobian (Moore-Penrose pseudo-inverse matrix) is a (scaled) weight vector

It can be used to fine tune the physical geometric model, such that the physical geometric model is tuned to be similar to.

Therefore, in one embodiment, a data-driven technique (the examples are discussed above) at 1400 is performed to derive the weights as discussed above. These calculations take multiple inputs. One of the inputs is a set value 1420 of a set-get process for a target having a physical instance of the unit cell of interest. As mentioned above, multiple instances of the target can be measured across one or more substrates, one or more instances of the target having different values of intentionally set values of the patterning process parameters than one or more other instances of the target. . An additional input is the measured optical information 1410 for that instance of the target at different setting values. In one embodiment, the optical information 1410 is a plurality of pupil representations, each corresponding to an instance of a target. The inputs 1410 and 1420 are then processed with a data-driven scheme to arrive at a weight 1430.

Weights 1430 are input to process 1440 to fine tune the physical geometric model using weights 1430. The process 1440 acquires a physical profile 1450 (used by the process 1440 to derive a physical profile model) for a unit cell or a physical profile model 1450 (used by the process 1440) for a unit cell. To obtain. In one embodiment, the physical profile is a derived nominal profile and/or a derived nominal profile model of a unit cell, as described above.

Process 1440 uses a physical geometric model to derive weights corresponding to weights 1430. Then, those weights are compared to weights 1430. Such comparison may involve matching sizes, statistical analysis, fitting evaluation, and the like. If significant differences exist (eg, by evaluating a comparison against a threshold), one or more parameters of the physical profile can be tuned. For example, one or more physical profile parameters (eg, CD, sidewall angle, material height, etc.) can be tuned such that the comparison result is closer or closer to a particular threshold, for example. In one embodiment, Hessian may be used to perform such fine tuning, or may be performed using a nonlinear solver (a solver containing one or more forward calls (e.g., Maxwell solver)). . Tuning and comparison can be repeated until the threshold is satisfied or passed. The tuned physical geometric model can then output an updated weight 1460 for use in combining it with the measured optical information of the target of interest to derive the patterning process parameter value.

15 shows a high level flow of another embodiment of a data-driven technique combined with a physical geometric model. If the physical geometric model exhibits similar behavior to the measured data, the physical geometric model can be used to predict the effect of process variations. Therefore, in one embodiment, the Hessian of the physical geometric model tunes the weights, and in order to obtain the weights used to tune the physical geometric model, the weight is ( More) can be used to make it orthogonal.

This approach using Hessian to tune the weights may be performed without the data-driven technique. That is, this technique of using Hessian to update weights may be performed together with the physical geometric model approach described in connection with FIG. 11. In this case, for example, the weights are such that the weights are (more) orthogonal to process variations that were not present in the data used to obtain the derived nominal profile and/or derived nominal profile model of the unit cell as described above. Can be tuned to Through this tuning, the weights become more robust against process variations not observed in the measured data used to generate the physical geometric model.

Therefore, in one embodiment, a data-driven technique (the examples are discussed above) at 1500 is performed to derive the weights as discussed above. These calculations take multiple inputs. One of the inputs is a set value 1510 of a set-get process for a target having a physical instance of the unit cell of interest. As mentioned above, multiple instances of the target can be measured across one or more substrates, one or more instances of the target having different values of intentionally set values of the patterning process parameters than one or more other instances of the target. . An additional input is the measured optical information 1505 for that instance of the target at different setting values. In one embodiment, optical information 1505 is a plurality of pupil representations, each corresponding to an instance of a target. The inputs 1505 and 1510 are then processed in a data-driven scheme to arrive at a weight 1515.

Weights 1515 are input to process 1520 to fine tune the physical geometric model using weights 1515. Process 1520 obtains a physical profile 1525 (used by process 1520 to derive a physical profile model) for a unit cell or a physical profile model 1525 (used by process 1520) for a unit cell. To obtain. In one embodiment, the physical profile is a derived nominal profile and/or a derived nominal profile model of a unit cell, as described above.

Process 1520 uses a physical geometric model to derive weights corresponding to weights 1515. Then, those weights are compared to the weights 1515. Such comparison may involve matching sizes, statistical analysis, fitting evaluation, and the like. If significant differences exist (eg, by evaluating a comparison against a threshold), one or more parameters of the physical profile can be tuned. For example, one or more physical profile parameters (eg, CD, sidewall angle, material height, etc.) can be tuned such that the comparison result is closer or closer to a particular threshold, for example. In one embodiment, Hessian may be used to perform such fine tuning, or may be performed using a nonlinear solver (a solver containing one or more forward calls (e.g., Maxwell solver)). . Tuning and comparison can be repeated until the threshold is satisfied or passed.

However, as can be appreciated, the patterning process may vary differently during execution and for different executions of the patterning process. Therefore, the data obtained for the data-driven technique does not take into account all possible patterning process variations. However, if a physical geometric model is tuned so that the model behaves similarly to the measured data, the physical geometric model can be used to predict the impact of process variations and adjust the weights accordingly.

Therefore, in one embodiment, the tuned physical geometric model 1530 is used, at 1535, to compute the Hessian of the tuned physical geometric model. Then, Hessian (1540) tunes the weights at 1545 and obtains the weights used to tune the physical geometric model, so that the weights are (more) for process variations that were not present in the data used in the data-driven technique. It can be used to be orthogonal (i.e. to be robust). In other words, the weights are tuned to increase the likelihood of producing accurate results when combined with measurement data from the substrate even if the substrate undergoes process variation.

A non-limiting example of how Hessian can be used to fine tune weights is described herein in the context of an overlay; Different patterning process parameters can also be used as appropriate. In this example, it is assumed that only one overlay type (eg, overlay in the X direction) is evaluated. Fine-tuning with multiple overlay types is also possible.

(길이 1 을 가짐)가 오버레이 응답에 대응한다고 가정된다. 그러면 벡터

를 찾기 위해서 다음 수학식을 푼다:In this embodiment using Hessian to fine tune the weights, the overlay response is estimated from measured data from one or more set-get substrates by applying a single value decomposition to this data. Eigenvector

It is assumed that (with length 1) corresponds to the overlay response. Then vector

Solve the following equation to find:

는 오버레이 파라미터에 대한 야코비안이고, 헤시안

는 열들이 프로세스 변동(예를 들어, CD, 재료 높이 등의 변동) 및 오버레이 파라미터에 대한 편도함수를 포함하는 행렬이다(야코비안 및 헤시안 양자 모두는 전술된 바와 같은 모델로부터 획득된다). 그러면, 결정된 벡터

는 업데이트된(예를 들어, 더 양호한) 모델을 얻기 위해서 모델 내의 비-오버레이 파라미터에 적용될 델타 파라미터에 대응한다.From here

Is the Jacobian for the overlay parameter, and Hessian

Is a matrix in which the columns contain partial derivatives for process variation (eg, variation in CD, material height, etc.) and overlay parameters (both Jacobian and Hessian are obtained from the model as described above). Then, the determined vector

Corresponds to the delta parameter to be applied to the non-overlay parameter in the model in order to obtain an updated (eg, better) model.

는 다음의 2차 테일러 전개식에 의해 규정될 수 있다:In order for the weights to be robust to the process variation (ie, orthogonal to the process variation), a subsequent technique can be used. Pupil

Can be defined by the following quadratic Taylor expansion:

는 오버레이 파라미터에 대한 야코비안이고,

는 열들이 프로세스 변동(예를 들어, CD, 재료 높이 등의 변동) 및 오버레이 파라미터에 대한 편도함수를 포함하는 행렬이다. 벡터

는 대응하는 프로세스 변동을 포함한다. 따라서, 오버레이 값 ο를 가지는 주어진 구조체 및 주어진 프로세스 변동 인스턴스

에 대하여, 퓨필은 (근사적으로)

와 같아진다. 이해될 수 있는 것처럼, 위의 공식은 이러한 기여분을 함께 추가함으로써 더 많은 오버레이 파라미터로 확장될 수 있다. 더욱이, 테일러 전개식의 더 높은 차수가 무시되기 때문에, 이러한 공식은 근사화이다.From here

Is the Jacobian for the overlay parameter,

Is a matrix in which the columns contain partial derivatives for process variation (eg, variation in CD, material height, etc.) and overlay parameters. vector

Contains the corresponding process variation. Thus, a given structure with overlay value ο and a given process variation instance

Regarding, the pupil is (approximately)

Becomes equal to As can be appreciated, the above formula can be extended to more overlay parameters by adding these contributions together. Moreover, this formula is an approximation because the higher order of the Taylor expansion equation is neglected.

의 펜로즈-무어 역행렬을 사용하여 계산된다. 오직 하나의 오버레이 파라미터만 있는 경우에, 가중치는

과 같아진다. 그리고 사실상, 퓨필과의 가중된 평균(내적)은 오버레이 값 ο(

)가 되고, 즉Now, if the impact of process variation is small, the weight is Jacobian

It is calculated using the Penrose-Moore inverse matrix. If there is only one overlay parameter, the weight is

Becomes equal to And in fact, the weighted average (dot product) with the pupil is the overlay value ο(

), that is

to be. However, if the impact of process variations is large, the overlay response changes as follows:

To make the weights robust against these fluctuations,

를 행렬

의 의사 역행렬의 제 1 행과 같게 만듦으로써 달성될 수 있다. 또는 다르게 말하면, 헤시안 행렬

는 반전되기 전에 야코비안에 연쇄된다. 이러한 방식으로, 가중치는 프로세스 변동에 직교하게 된다(하지만 정밀도가 일부 희생됨).to be. This is the weight

Matrix

This can be achieved by making it equal to the first row of the pseudo-inverse matrix of. Or in other words, the Hessian matrix

Is chained to Jacobian before being reversed. In this way, the weights are orthogonal to the process variation (but at the expense of some precision).

Thus, tuned weights 1550 from tuning 1545 are output for use in combining with the measured optical information of the target of interest to derive the patterning process parameter values.

16 shows a high level flow of another embodiment of a data-driven technique combined with a physical geometric model. In this embodiment, the data input to the data-driven technique is synthetic optical information (e.g., pupil representation, including process variation (e.g., patterning process variation can be obtained from CD measurements) for the patterning process). ). Synthetic optical information can be used alone or in combination with measured optical information to find new weights using data-driven techniques.

Therefore, in one embodiment, a data-driven technique (the examples are discussed above) at 1500 is performed to derive the weights as discussed above. These calculations take multiple inputs. One of the inputs is a set value 1510 of a set-get process for a target having a physical instance of the unit cell of interest. As mentioned above, multiple instances of the target can be measured across one or more substrates, one or more instances of the target having different values of intentionally set values of the patterning process parameters than one or more other instances of the target. . An additional input is the measured optical information 1505 for that instance of the target at different setting values. In one embodiment, optical information 1505 is a plurality of pupil representations, each corresponding to an instance of a target. The inputs 1505 and 1510 are then processed in a data-driven scheme to arrive at a weight 1515.

Weights 1515 are input to process 1520 to fine tune the physical geometric model using weights 1515. Process 1520 obtains a physical profile 1525 for a unit cell (process 1520 uses to derive a physical profile model) or a physical profile model 1525 for a unit cell (process 1520 uses). do. In one embodiment, the physical profile is a derived nominal profile and/or a derived nominal profile model of a unit cell, as described above.

Process 1520 uses a physical geometric model to derive weights corresponding to weights 1515. Then, those weights are compared to the weights 1515. Such comparison may involve matching sizes, statistical analysis, fitting evaluation, and the like. If significant differences exist (eg, by evaluating a comparison against a threshold), one or more parameters of the physical profile can be tuned. For example, one or more physical profile parameters (eg, CD, sidewall angle, material height, etc.) can be tuned such that the comparison result is closer or closer to a particular threshold, for example. Tuning and comparison can be repeated until the threshold is satisfied or passed.

는 위의 수학식 8 에 상이한 오버레이 값 ο와 상이한 파라미터 변동

를 대입함으로써 생성될 수 있는데, 여기에서 가중치는

에 대응한다. 전술된 수학식 8 이 오버레이 파라미터에 직결되지만, 이러한 기법은 그러한 기여분을 함께 추가함으로써 더 많은 오버레이 파라미터로 확장될 수 있다. 더욱이, 테일러 전개식의 더 높은 차수가 무시되기 때문에, 수학식 8 을 사용하는 기법은 근사화이다. 데이터(1620)는, 예를 들어 프로세스 변동의 종류 및 치수를 기술하는 정보(예를 들어, 오버레이, CD 등이 어떤 퍼센티지만큼 변할 수 있다는 표시)를 포함할 수 있다. 데이터(1620)는 패터닝 프로세스에서의 측정, 예를 들어 오버레이, CD 등의 측정에 의하여 획득될 수 있다. 따라서, 데이터(1620)는 기대된 프로세스 변동을 포함하는 시뮬레이션된 광학적 정보(1630)를 생성하도록, 헤시안(1600)과 함께 사용된다. 합성 광학적 정보(1630)는 합성 광학적 정보(1630)와 연관된 하나 이상의 연관된 추정된 설정 값을 더 포함할 수 있다. 그러면, 합성 광학적 정보(1630)(및 임의의 연관된 설정 값)는, 데이터-구동 기법을 사용하여 새로운 가중치를 찾기 위해서, 분석을 위하여 홀로 또는 측정된 광학적 정보와 조합되어 데이터-구동 기법(1500)에 입력된다.Therefore, in one embodiment, the tuned physical geometric model 1530 is used, at 1535, to compute the Hessian of the tuned physical geometric model. Then, Hessian 1600 is used to generate at 1610 synthetic optical information (eg, one or more pupil representations). Synthetic optical information is simulated optical information. The synthetic optical information is intended to mimic one or more expected process variations in the patterning process. In one embodiment, data 1620 relating to one or more process variations in the patterning process may be used in combination with Hessian 1600 to derive synthetic optical information. In one embodiment, synthetic pupil

Is a different overlay value ο and a different parameter variation in Equation 8 above

Can be created by substituting for, where the weight is

Corresponds to Equation 8 described above is directly connected to the overlay parameter, but this technique can be extended to more overlay parameters by adding those contributions together. Moreover, since the higher order of the Taylor expansion equation is neglected, the technique using equation 8 is an approximation. The data 1620 may include, for example, information describing the type and dimension of process variation (eg, an indication that an overlay, CD, etc. may vary by a certain percentage). The data 1620 may be obtained by measurement in a patterning process, for example, an overlay, a CD, or the like. Accordingly, data 1620 is used in conjunction with Hessian 1600 to generate simulated optical information 1630 including expected process variations. The composite optical information 1630 may further include one or more associated estimated set values associated with the composite optical information 1630. The synthesized optical information 1630 (and any associated set values) is then combined with the measured optical information alone or for analysis to find a new weight using the data-drive technique, and the data-drive technique 1500. Is entered in

17 shows a high level flow of another embodiment of a data-driven technique combined with a physical geometric model. This embodiment is similar to the embodiment of Fig. 16, except that a forward arc is made with a nonlinear solver (e.g. Maxwell solver) for all process variations to obtain synthetic optical information instead of calculating Hessian. Do.

Therefore, in one embodiment, a data-driven technique (the examples are discussed above) at 1500 is performed to derive the weights as discussed above. These calculations take multiple inputs. One of the inputs is a set value 1510 of a set-get process for a target having a physical instance of the unit cell of interest. As mentioned above, multiple instances of the target can be measured across one or more substrates, one or more instances of the target having different values of intentionally set values of the patterning process parameters than one or more other instances of the target. . An additional input is the measured optical information 1505 for that instance of the target at different setting values. In one embodiment, optical information 1505 is a plurality of pupil representations, each corresponding to an instance of a target. The inputs 1505 and 1510 are then processed in a data-driven scheme to arrive at a weight 1515.

Weights 1515 are input to process 1520 to fine tune the physical geometric model using weights 1515. Process 1520 obtains a physical profile 1525 for a unit cell (process 1520 uses to derive a physical profile model) or a physical profile model 1525 for a unit cell (process 1520 uses). do. In one embodiment, the physical profile is a derived nominal profile and/or a derived nominal profile model of a unit cell, as described above.

Process 1520 uses a physical geometric model to derive weights corresponding to weights 1515. Then, those weights are compared to the weights 1515. Such comparison may involve matching sizes, statistical analysis, fitting evaluation, and the like. If significant differences exist (eg, by evaluating a comparison against a threshold), one or more parameters of the physical profile can be tuned. For example, one or more physical profile parameters (eg, overlay, CD, sidewall angle, etc.) may be tuned such that the result of the comparison is closer or closer to a particular threshold, for example. Tuning and comparison can be repeated until the threshold is satisfied or passed.

Therefore, in one embodiment, the tuned physical geometric model 1700 is used at 1720 to compute the composite optical information as described above. Similar to that discussed above, data 1710 related to one or more process variations in the patterning process can be used in combination with the tuned physical geometric model 1700 to derive synthetic optical information. For example, the data 1710 may include information describing the type and dimension of process variation (eg, an indication that an overlay, CD, etc. may vary by a certain percentage). The data 1710 may be obtained by measurement in a patterning process, for example, an overlay, a CD, or the like. As mentioned above, the process in process 1720 can obtain synthetic optical information using a forward arc to a nonlinear solver (eg, Maxwell solver) for process variations. Accordingly, data 1710 is used with the tuned physical geometric model 1700 to generate simulated optical information 1730 that includes the expected process variation. The composite optical information 1730 may further include one or more associated estimated set values associated with the composite optical information 1730. The synthesized optical information 1730 (and any associated set values) is then combined with the measured optical information alone or for analysis to find a new weight using the data-drive technique, and the data-drive technique 1500. Is entered in

In FIGS. 10A-10C, a relatively simple example of a unit cell is provided, in which essentially only one direction of overlay caused a change in the symmetry of the unit cell. In particular, in the unit cells of FIGS. 10A to 10C, an overlay change in the X direction causes a change in symmetry/asymmetry of the unit cell, but an overlay change in the Y direction does not cause a change in the symmetry of the unit cell. This is the result of the unit cell of FIGS. 10A-10C having essentially two structures 1000, 1005 constructed in a particular geometrical manner in which the overlay in only one direction caused a change in the symmetry of the unit cell. Of course, this can be designed in this way by choosing the appropriate structure. However, an existing structure, such as a device structure, can be identified having a specific geometry such that essentially only one orientation of the overlay causes a change in the symmetry of the unit cell. Therefore, a variety of unit cells can be selected or designed that essentially allow determining the overlay in only one direction (but not the X direction).

However, preferably, a unit cell configured to cause two or more different overlays can be identified or designed if a change in the symmetry of the unit cell occurs. In one embodiment, different overlays may be in different directions. Specifically, in one embodiment, the first overlay may be in the X direction, while the second overlay may be in the Y direction. In one embodiment, different overlays may each exist between different combinations of structures or portions of a unit cell. In one embodiment, such structures may be on the same and/or different layers of the target. Specifically, in one embodiment, the first overlay may be between the first structure and the second structure of the unit cell, and the second overlay may be the first structure (or second structure) and the third structure of the unit cell. It may be between or between the third structure and the fourth structure of the unit cell. In this case, the first overlay and the second overlay may be in the same direction. Naturally, there may be different overlays in different directions and different combinations of overlays from combinations of structures of the unit cell. For example, the first overlay can be in the X direction with respect to the first structure of the first layer and the second structure of the underlying second layer, and the second overlay is below the first structure and the second layer of the first layer. It may be in the Y direction with respect to the third structure of the third layer. Thus, multiple combinations of overlays can be determined through proper identification or design of unit cells (and thus targets).

Moreover, as can be appreciated, the determination of the overlay in the X and Y directions can make it possible to determine the total overlay (X and Y directions) through an appropriate combination. Similarly, in order to be able to determine the total overlay for a number of different structures that may have an overlay between them, the overlay for each of those structures needs to be determined. Therefore, as an example, for a unit cell having 4 distinct structures in 4 layers (one of the layers being the reference layer) where an overlay may occur between them, it now makes it possible to determine the total overlay for the unit cell. To do this, six overlays (X and Y for each layer) can be determined. Of course, in order to reach one or more different overlays of interest between the four layers, sub-combinations can be determined as needed.

18 shows an exemplary embodiment of a multiple overlay unit cell of a target. Similar to the unit cell of FIGS. 10A to 10C, this unit cell includes a first structure 1000 and a second structure 1005. Additionally, this unit cell has a third structure 1800 in a layer over the first and second structures 1000 and 1005 in the Z direction in this embodiment. In this embodiment, this asymmetry of unit cells may be created by one or more different overlays. For example, a relative shift between structure 1005 and structure 1800 in the X direction may provide an overlay in the X direction that results in asymmetry. As another example, a relative shift between the structure 1005 and the structure 1000 in the Y direction may provide an overlay in the Y direction resulting in asymmetry. As an additional example, the relative shift between the structure 1000 and the structure 1800 in the Y direction may provide an additional overlay in the Y direction that results in asymmetry.

19 shows a further exemplary embodiment of a target multiple overlay unit cell. Similar to the unit cell of FIGS. 10A to 10C, this unit cell includes a first structure 1000 and a second structure 1005. Additionally, similar to the unit cell of FIG. 18, this unit cell has a third structure 1800 in a layer over the first and second structures 1000, 1005 in the Z direction in this embodiment. Furthermore, this unit cell has a fourth structure 1900 in a layer over the first, second and third structures 1000, 1005, 1800 in the Z direction in this embodiment. Similar to the unit cell of FIG. 18, in this embodiment, the asymmetry of this unit cell may be created by one or more different overlays. For example, a relative shift between structure 1005 and structure 1800 in the X direction may provide an overlay in the X direction that results in asymmetry. As another example, the relative shift between the structure 1005 and the structure 1900 in the X direction may provide an overlay in the X direction that results in asymmetry. As another example, a relative shift between the structure 1005 and the structure 1000 in the Y direction may provide an overlay in the Y direction resulting in asymmetry. As an additional example, the relative shift between the structure 1000 and the structure 1800 in the Y direction may provide an additional overlay in the Y direction that results in asymmetry.

Thus, in one embodiment, measurement of the illuminated physical instance of the unit cell of FIG. 18 or 19 would in fact provide optical information that could potentially include a number of different overlays if there were a number of different overlays. For example, referring to FIG. 18, the symmetry of the unit cell of FIG. 18 represents a zero overlay, and the X and Y shifts of the structure 1005 from the zero overlay position relative to the overlying structure (e.g., 0 , A shift in a direction other than 90, 180, or 270 degrees), such a shift is a relative shift between the structures 1005 and 1800 in the X direction and the structures 1005 and 1000 in the Y direction. It will result in asymmetry due to the relative shift between. Therefore, it would be desirable to determine the overlay of both for the structure 1005 in the X and Y directions (the combination will give the total overlay of the structure 1005).

As will now be discussed, from the optical property value, the value of the first overlay for the physical instance of the unit cell can be determined separately from the second overlay that is for the physical instance of the unit cell and also obtainable from the same optical property value. A technique is provided, wherein the first overlay is in a different direction than the second overlay (e.g., an X-direction overlay and a Y-direction overlay) or between portions of a unit cell in a different combination than the second overlay (e.g., The first overlay is between the structure 1005 and the structure 1800 and the second overlay is between the structure 1005 and the structure 1000 or between the structure 1000 and the structure 1800, the first overlay and the first overlay 2 Overlays can be in the same orientation).

That is, in one embodiment, the weight is determined to decouple the first overlay information in the optical property value from the second (or more) overlay information in the same optical property value. Thus, in one embodiment, by applying a specially selected weight, combining the weight with an optical characteristic value will provide a specific overlay of interest that is distinct from other possible overlay information at the same optical characteristic value. As a result, the weights will highlight the overlay of interest and weaken one or more other overlays. Of course, a different set of weights can be configured for each overlay of interest so that optical property values can be processed to provide a different value for each of the different overlays of interest.

This technique will be described for different sets of weights in FIG. 20. The graph of FIG. 20 provides a graphical representation of this technique, but in practice, such a graph does not need to be constructed since all processing can be done mathematically without the need to create a graph. Furthermore, this technique is described for the model of FIG. 11. However, models (and other associated techniques) described with respect to other figures herein may also be used.

Furthermore, this example is provided for deriving a linear version of the weights from the model. That is, in one embodiment, the weights are derived from Jacobian (the Moore-Penrose pseudo inverse matrix).

Therefore, in this linear case, in order to reconstruct a specific parameter, such as an overlay in a specific direction, the Jacobian can be inverted. However, how the heat of the parameter of interest correlates with the residual heat determines how easy it will be to reconstruct these parameters.

은 유닛 셀 내의 제 1 관심 오버레이(예를 들어, X-방향 오버레이)를 나타내고, 제 2 오버레이 벡터

는 제 2 관심 오버레이(예를 들어, Y-방향 오버레이)를 나타낸다. 이해될 수 있는 것처럼, 추가적인 관심 오버레이에 대해서는 추가적인 벡터가 생성될 수 있다.Therefore, for example, if you have a nominal profile model for the unit cell of interest (eg, the unit cell of FIG. 18), at least two vectors can be generated. First overlay vector

Represents the first overlay of interest (e.g., X-direction overlay) in the unit cell, and the second overlay vector

Represents a second overlay of interest (eg, Y-direction overlay). As can be appreciated, additional vectors can be created for additional overlays of interest.

Furthermore, for each of the two overlay vectors, one or more pixels of the pupil representation corresponding to the expected measurement of the physical instance of the unit cell are selected. In this embodiment, a pair of pixels is selected for each overlay vector, with each pair of pixels comprising a symmetrically positioned pixel as described above. Preferably, a pair of pixels is selected from the asymmetric radiation distribution portion of the pupil representation as discussed above.

은 제 1 오버레이 벡터에 대한 제 1 관심 오버레이의 변화(모든 다른 파라미터는 변하지 않게 유지되고, 즉 제 2 관심 오버레이는 변화가 없음)에 대한, 픽셀의 쌍에서의 응답(이러한 경우에, 쌍을 이루는 픽셀들 사이의 비대칭 신호)에 대응한다. 이러한 응답은 공칭 프로파일 모델을 사용하여, 제 1 관심 오버레이의 변화(예를 들어, 1 nm 변화)를 유도한 후 그러한 변화에 대한 픽셀의 쌍에서의 광학적 응답(예를 들어, 세기)을 계산함으로써 생성될 수 있다.Now, the first overlay vector

Is the response in a pair of pixels (in this case, paired) to a change in the first overlay of interest to the first overlay vector (all other parameters remain unchanged, i.e. the second overlay of interest remains unchanged). Corresponds to an asymmetric signal between pixels). This response is determined by using a nominal profile model to derive a change in the first overlay of interest (e.g., 1 nm change) and then calculate the optical response (e.g., intensity) in a pair of pixels to that change. Can be created.

는 제 2 오버레이 벡터에 대한 제 2 관심 오버레이의 변화(모든 다른 파라미터는 변하지 않게 유지되고, 즉 제 1 관심 오버레이는 변화가 없음)에 대한, 픽셀의 쌍에서의 응답(이러한 경우에, 쌍을 이루는 픽셀들 사이의 비대칭 신호)에 대응한다. 이러한 응답은 공칭 프로파일 모델을 사용하여, 제 2 관심 오버레이의 변화(예를 들어, 1 nm 변화)를 유도한 후 픽셀의 쌍에서의 광학적 응답(예를 들어, 세기)을 계산함으로써 생성될 수 있다.Similarly, the second overlay vector

Is the response in a pair of pixels (in this case, paired) to a change in the second overlay of interest to the second overlay vector (all other parameters remain unchanged, i.e. the first overlay of interest remains unchanged). Corresponds to an asymmetric signal between pixels). This response can be generated by using a nominal profile model to derive a change (e.g., 1 nm change) of the second overlay of interest and then calculate the optical response (e.g., intensity) in a pair of pixels. .

는 제 1 픽셀 쌍의 대칭적으로 위치된 픽셀들 사이의 비대칭 세기(Ii - Ii')에 대응하고, 수직 축

는 제 2 픽셀 쌍의 대칭적으로 위치된 픽셀들 사이의 비대칭 세기(Ii - Ii')에 대응한다. 그러므로, 도 20 은 두 개의 고도로 상관된 벡터

및

를 보여준다.The resulting vector is shown in Fig. 20, the horizontal axis

Corresponds to the asymmetry intensity (Ii-Ii') between symmetrically located pixels of the first pixel pair, and the vertical axis

Corresponds to the asymmetric intensity (Ii-Ii') between symmetrically located pixels of the second pixel pair. Therefore, Figure 20 is the two highly correlated vectors

And

Show

은 벡터

에 직교하는 벡터인 벡터

상에 역-투영되어 벡터

를 형성하고, 투영된 벡터

의 길이는 벡터

및

사이의 각도

의 코사인으로 나누게 된다. 그러면 이러한 벡터는 픽셀 쌍(확장에 의하면 퓨필 표현 내의 다른 픽셀 쌍)의 세기로부터 제 1 관심 오버레이를 격리시키는 것을 돕는다.Therefore, in order to decouple and separate the contributions of the first and second overlay of interest to the pair of pixels, the vector

Silver vector

A vector orthogonal to

Vector back-projected onto

And the projected vector

The length of the vector

And

Angle between

Is divided by the cosine of This vector then helps to isolate the first overlay of interest from the intensity of the pair of pixels (the other pair of pixels in the pupil representation by extension).

는 벡터

에 직교하는 벡터인 벡터

상에 역-투영되어 벡터

를 형성하고, 투영된 벡터

의 길이는 벡터

및

사이의 각도

의 코사인으로 나누게 된다. 그러면 이러한 벡터는 픽셀 쌍(확장에 의하면 퓨필 표현 내의 다른 픽셀 쌍)의 세기로부터 제 2 관심 오버레이를 격리시키는 것을 돕는다.Additionally or alternatively, a vector

The vector

A vector orthogonal to

Vector back-projected onto

And the projected vector

The length of the vector

And

Angle between

Is divided by the cosine of This vector then helps to isolate the second overlay of interest from the intensity of the pair of pixels (the other pair of pixels in the pupil representation by extension).

은

의 Si를 가지는 제 1 픽셀 쌍 및

의 Si를 가지는 제 2 픽셀 쌍에서의 제 1 관심 오버레이의 변화에 대한 응답에 대응할 수 있다. 이와 유사하게, 제 2 오버레이 벡터

는 제 2 관심 오버레이의 변화에 대한 그러한 제 1 및 제 2 픽셀 쌍에서의 응답에 대응할 수 있다. 따라서, 벡터

및/또는 벡터

가 구성될 수 있다; 여기에서 양자 모두는 예시를 위해서 구성된다. 벡터

및 벡터

는

에 대응하는 제 1 픽셀 쌍에 대응하는 세기

에 관하여 그리고

에 대응하는 제 2 픽셀 쌍에 대응하는 세기

에 관하여 규정된다. 그러므로, 벡터

및 벡터

는 다음과 같이 특정될 수 있다:Therefore, referring again to Equations 3 and 4, Si denotes an asymmetric intensity (Ii-Ii') between symmetrically positioned pixels of a pixel pair. Therefore, the first overlay vector

silver

A first pair of pixels having Si of and

It may correspond to a response to a change in the overlay of the first interest in the second pixel pair with Si of. Similarly, the second overlay vector

May correspond to a response at such a first and second pixel pair to a change in the second overlay of interest. Thus, the vector

And/or vector

Can be configured; Both here are configured for illustration purposes. vector

And vector

Is

Intensity corresponding to the first pair of pixels corresponding to

About and

Intensity corresponding to the second pair of pixels corresponding to

Is defined in relation to. Therefore, the vector

And vector

Can be specified as follows:

,

, 및 벡터

및

에 기초하여 다음과 같이 규정될 수 있다:Therefore, now in the linear context described above and referring to Equation 4, the overlay value of the first overlay of interest is now

,

, And vector

And

On the basis of, it can be defined as:

,

및 벡터

및

에 기초하여 다음과 같이 규정될 수 있다Additionally or alternatively, the overlay value of the second overlay of interest is now

,

And vector

And

Can be defined as follows on the basis of

및

각각에 대하여, 다음과 같다:Therefore, from Equation 14, the weight for determining the first interest overlay is

And

For each, it is as follows:

,

,

및

각각에 대하여 다음과 같다:Furthermore, from Equation 15, the weight for determining the second interest overlay is

And

For each:

의 세트(

)에 도달하고 및/또는 제 2 관심 오버레이에 대한 가중치

의 세트(

)에 도달하기 위하여, 이것은 퓨필 표현 내의 픽셀 쌍의 전부, 또는 실질적으로 전부에 대해서 반복될 수 있다. 그러면, 이들 중 하나 또는 양자 모두가 수학식 4 에 따라서 측정된 광학 특성 값에 적용되어, 각각의 관심 오버레이에 대한 오버레이 값에 도달할 수 있다. 물론, 하나 이상의 추가적 관심 오버레이가 평가될 수 있고 하나 이상의 적절한 가중치 세트가 그들로부터 결정된다. 이해될 수 있는 것처럼, 일 실시예에서, 상이한 관심 오버레이 모두에 대한 감도(예를 들어, 야코비안)는 특정 관심 오버레이에 대한 가중치 정의에 포함된다.Therefore, as can be understood, the weight for the first interest overlay

Set of (

) And/or weights for the second overlay of interest

Set of (

), this can be repeated for all, or substantially all, of the pair of pixels in the pupil representation. Then, one or both of these can be applied to the measured optical property values according to Equation 4, to reach the overlay values for each overlay of interest. Of course, one or more additional interest overlays can be evaluated and one or more appropriate sets of weights are determined from them. As can be appreciated, in one embodiment, the sensitivity (eg, Jacobian) for all different overlays of interest is included in the weight definition for a particular overlay of interest.

Therefore, for example, if there is a shift in the layer shift in the X and Y directions, it can cause a change in symmetry (e.g., asymmetry occurs or asymmetry becomes severe, or the asymmetric unit cell becomes symmetric) 4 For a unit cell with 3 layers (one of the layers is a reference layer), now 6 vectors can be created (each associated with a different pair of pixels), and 6 vectors are the X-direction overlay vectors for each of the layers. And a Y-direction overlay vector for each of the layers. Thus, there can be six sets of weights to derive each overlay. Of course, if one of the vectors is not of interest, it is not necessary to derive all of the weight sets (but in one embodiment, the sensitivity (e.g. Jacobian) for all of the different overlays of interest) is Included in the weight definition). Then, any other overlay can be determined by a suitable mathematical combination of two or more of these overlays.

As can be appreciated, a particular shift of a layer within a unit cell will not cause a change in symmetry, so the overlay corresponding to that shift cannot be determined from the unit cell. Therefore, it is clear that no vector will be specified for this shift. Therefore, referring to FIG. 18 as an example, three vectors can be defined for a corresponding unit cell-one for an X-direction overlay and two for a different Y-direction overlay. Therefore, one set of weights can be determined that will provide an overlay in the X-direction when combined with the measured optical characteristic values. Alternatively, one set of weights that will provide one of the Y-direction overlays when combined with the measured optical property values can be determined, and/or the other of the Y-direction overlays when combined with the measured optical property values One set of weights can be determined to provide them. Of course, all three sets of weights or only two may be determined.

The above discussion has focused on targets formed by one or more instances of a symmetrical unit cell made up of the structures of the device. Such a target may cause the on-product value of the patterning process parameter to be determined through an on-product measurement of radiation redirected by the on-product target. However, as described above, the target need not consist solely of device structures. In other words, a non-product target may be provided whose structure does not include a device structure. For example, in one embodiment, the target may be specially created with a structure that is not used to form the device, but rather is used only for measurement. Such a target may be provided, for example, in a scribe lane away from the device (and thus to a portion of the device patterning pattern away from the device pattern). In one embodiment, a target may be provided between device patterns (and thus provided between features of the device pattern of the patterning device pattern). Where appropriate, a non-product target may include one or more device structures and one or more specially created structures that are not used to form the device, but rather are used only for measurement.

Non-product targets may be useful, for example, if the patterning process parameters are being determined for device patterns that cannot provide symmetric unit cell instances. As another example, a non-product target is being determined for a portion of a device pattern that does not have a symmetrical unit cell as described above, e.g., the patterning process parameter can provide a measure of that patterning process parameter. , Can be useful. For example, there may be cases where it is desired that the structure for the overlay after etching is determined using the symmetric unit cell method described above, but does not have symmetry. For example, a logic circuit or structure has many process layers/steps that can each introduce a different overlay component that can break the symmetry of the structure. In the case of a logic circuit, for example, a measurement on the device pattern cannot be performed due to the lack of symmetric unit cells of the logic circuit structure in general.

As a further example, non-product targets can be used in association with a device pattern that can provide a symmetric unit cell instance (even if the unit cell can provide a measure of all of the patterning process parameters of interest). For example, this may be the case where the device pattern is complex, which may require a long computation time. Furthermore, the device pattern can provide potential cross-talk with signals of patterning process parameters that are not of interest. As an example, the pupil correlation of different overlay components may be so great that it may be impossible to separate different overlay errors.

Thus, a non-product target may be used with a device pattern that has instances of unit cells symmetric with respect to the beam spot or device patterns that cannot provide instances of symmetric units with respect to the beam spot.

Thus, in one embodiment, a non-product target may be designed such that a particular type of patterning process parameter of interest (eg, an overlay) breaks the (pupil) symmetry of a particular type of a non-product target; This is similar to the technique described above. And, similarly as discussed above, the overlay will be the focus of the discussion, but one or more patterning process parameters other than the overlay may be determined.

Of course, in order for a non-product target to provide a measure of the patterning process parameter, the non-product target will follow those process steps that are considered to be the primary contributor to the patterning process parameter of interest. Thus, as discussed above, if, for example, an overlay between two structures created in a separate patterning process is of interest, then the non-product target is in each of the separate patterning processes and preferably the same or comparable process. Contains the structure created in.

Furthermore, breaking any type of geometric symmetry (eg, Y-symmetric) breaks the same type of symmetry in the pupil domain. Therefore, non-product targets can be designed for a specific type of geometric symmetry, such that the corresponding specific patterning process parameter value breaks the symmetry. For example, the Y-symmetric is broken by the X-overlay. Furthermore, if there is symmetry in two or more directions, different types of patterning process parameters (e.g., different types of overlays, such as overlays on X and overlays on Y) are designed to break different types of symmetry. When used, the induced asymmetry can be monitored (depending on the type of symmetry involved) to determine one patterning process parameter (eg overlay) at a time.

Non-product targets can have one or more advantages. For example, a non-product target design may have a reduced or minimized pupil correlation when compared to using a measurement of radiation from an on-product target, as a result of which the patterning process parameter of interest is further reduced from the measured radiation. Easily determined. In one embodiment, the non-product target design may reduce or minimize cross-talk between different types of the same patterning process parameter or between different types of patterning process parameters. Thus, a cleaner signal can be obtained. Non-product target designs may have the advantage of measuring patterning process parameters for device patterns that do not have instances of symmetric unit cells with respect to the beam spot. Thus, non-product target design allows the measurement and determination techniques described herein to be extended to applications such as advanced memory and/or logic circuits where the device pattern may not have useful symmetrical unit cell instances. do. Non-product target designs can have a relatively simplified structure, as a result of which modeling can be facilitated, for example as described herein. This makes it easier to separate and determine two or more patterning process parameter types from a single target. Furthermore, the non-product target design can be specifically configured to determine only a single patterning process parameter type or only a specific combination of patterning process parameter types.

However, oversimplification of non-product target designs may eliminate significant contributors to patterning process parameters (eg overlays). To mitigate this risk, non-product target designs should take substantially the same process steps as device product patterns. Furthermore, the main contributors to the patterning process parameters of interest should be recognized so that they can be differentiated into non-product target designs and/or and associated models.

Therefore, similar to the on-product target design, one embodiment of a non-product target design is defined with respect to a unit cell comprising a structure having geometric symmetry. In one embodiment, the symmetry may be in a first direction (eg, X-direction), a second orthogonal direction (eg, Y-direction), or both. In one embodiment, the unit cell is created so that the symmetry is broken if there is a change in the physical composition of the structure within the unit cell, which can cause specific radiation that can be processed to determine the value of the patterning process parameter of interest as described above. Causes distribution. Thus, a unit cell substantially as a metrology target, in one embodiment, retains the smallest area of the structure used to provide a signal for determining the patterning process parameter of interest.

In one embodiment, the non-product target design comprises structures created in at least two patterning processes (e.g., at least two executions of the same type of patterning process, at least two executions of different types of patterning processes, etc.) do. In one embodiment, if the execution of a plurality of patterning processes results in structures in different layers for which the patterning process parameter of interest is determined, the non-product target design unit cell comprises a structure from each of the plurality of layers of interest. In one embodiment, if the patterning process execution results in a structure in the same layer for which the patterning process parameter of interest is determined, the non-product target design unit cell includes one structure from each of the different applicable patterning process executions of interest. In one embodiment, the first structure created by the first patterning process and/or the second structure created by the second patterning process are not used to create the functional aspect of the device pattern.

Therefore, in one embodiment and for a unit cell, structures resulting from multiple patterning processes together form one instance of a unit cell and the unit cell has geometric symmetry in its nominal physical configuration, where the unit cell has a nominal physical configuration. In a different physical configuration than have features that cause asymmetry in the unit cell due to, for example, a relative shift in pattern placement in the first patterning process, the second patterning process and/or other patterning processes. One example of such a feature is a feature that causes asymmetry in a unit cell in response to an offset of a structure in one layer to a structure in another layer.

In one embodiment, the non-product target design includes repetition of unit cells. That is, in one embodiment, a beam spot on a physical instance of a non-product target will illuminate a plurality of instances of unit cells that fill that beam spot. In one embodiment, the non-product target design is at least 4 instances, at least 8 instances, at least 10 instances, at least 20 instances, at least 40 instances, at least 80 instances, at least 100 instances, at least It includes 200 instances, at least 400 instances, or at least 1000 instances.

In one embodiment, the non-product target created on the substrate has a small size. For example, a non-product target may have an area of 100 square microns or less, 50 square microns or less, or 25 square microns or less. In one embodiment, the non-product target has a cross-wise dimension of 10 microns or less or 5 microns or less. In one embodiment, the beam spot for a non-product target has a transverse dimension that is less than the maximum transverse dimension of the target. In one embodiment, the beam spot for the non-product target has a transverse dimension of 10 microns or less, 5 microns or less, or 2 microns or less. In one embodiment, the beam spot for the non-product target has a cross-sectional area of 100 square microns or less, 50 square microns or less, or 25 square microns or less. In one embodiment, the unit cell of the non-product target has an area of 250,000 square nanometers or less, 150,000 square nanometers or less, 100,000 square nanometers or less, or 50,000 square nanometers or less. In one embodiment, the unit cell of the non-product target has a transverse dimension of 500 nanometers or less, 300 nanometers or less, 200 nanometers or less, or 150 nanometers or less. In one embodiment, the unit cell of the non-product target has a smaller size than the unit cell of the device pattern associated with the non-product target.

In one embodiment, the unit cell is a feature of a device manufactured using a first patterning process (e.g., a structure, voids, etc.) and a feature of a device manufactured using a second patterning process (e.g., a structure , Voids, etc.) corresponding features (eg, structures, voids, etc.). For example, the structure of the unit cell is created by a first patterning process that creates a corresponding device feature of the device, and another structure of the unit cell is created by a second patterning process that creates a corresponding device feature of the device. . In one embodiment, one or more features created within a unit cell share important process steps of the feature within the device in which the unit cell feature is being used to determine the patterning process parameter. In one embodiment, a feature of the unit cell created by each corresponding patterning process is one or more features of the device extending or elongated in a direction essentially parallel to, for example, a feature (e.g., line) of the unit cell. Corresponds to (for example, a structure such as a line). Thus, for example, a unit cell comprising a structure extending in the Y-direction can be used to determine the overlay of the corresponding structure in the device extending in the Y-direction.

In one embodiment, as further described in the examples described below, the unit cell makes it possible to determine several different types of the same patterning process parameter (eg, overlay). For example, a unit cell enables determination of two or more types of overlays, three or more types of overlays, and so on. For example, in addition to the type of overlay in different directions (eg, X and Y), the unit cell may allow overlays between different combinations of features and/or between different combinations of layers to be determined.

In one embodiment, the unit cell has features with dimensions (eg, width and/or pitch) comparable to a corresponding feature of the device. Comparable dimensions are the same or within ±5% from the device feature dimension (i.e., 95% to 105% of the device feature dimension), within ±10% from the device feature dimension, within ±15% from the device feature dimension, and from the device feature dimension. It means within ±20% and within ±25% from the device feature dimensions. In one embodiment, the dimensions of one or more unit cell features may be selected to improve the measurement signal and thus not match the corresponding dimensions of the features of the device pattern. This can be done, for example, by evaluating the sensitivity of the signal output to changes in the dimensions of the target feature, so the dimensions can be chosen to maximize the signal in a particular situation, or to provide a signal that meets or crosses a threshold.

In one embodiment, a non-product target may be used in conjunction with an on-product target. For example, the overlay can be determined using a non-product target, and the result can be fed forward to determine the overlay using an on-product target.

Referring to FIG. 21, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 21A, an example of a unit cell 2000 is shown. The unit cell 2000 includes a structure 2010 generated in a first patterning process (a plurality of lines 2010 in this case) and a structure 2020 generated in a second patterning process (in this case, a second plurality of lines ( 2020)). The anchor 2030 is marked to show the symmetry of the unit cell. In this case, the unit cell 2000 has symmetry in the Y direction. FIG. 21A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

In one embodiment, structure 2010 corresponds to a feature of a device fabricated using a first patterning process. In other words, the structure 2010 will be created by a first patterning process that creates a corresponding device feature of the device. For example, the creation of structure 2010 corresponds to a comparable creation of the structure within the device. Similarly, in one embodiment, structure 2020 corresponds to a feature of a device fabricated by a second patterning process. In other words, structure 2020 will be created by a second patterning process that creates a corresponding device feature of the device. For example, the creation of structure 2020 corresponds to a comparable creation of a structure in the device. Thus, in one embodiment, the structure 2010 is, for example, one or more features of the device (e.g., lines) extending in a direction essentially parallel to the features (e.g., lines) of the structure 2010. Structure). Similarly, structure 2020 may be applied to one or more features (e.g., a structure such as a line) of the device extending in a direction essentially parallel to, for example, a feature (e.g., a line) of structure 2020. Corresponds. In one embodiment, structure 2010 is created on a different layer than structure 2020. Therefore, in one embodiment, structures 2010 and 2020 extending in the Y-direction may be used to determine the overlay of the corresponding structure of the device extending in the Y-direction.

As mentioned above, in one embodiment, structures 2010 and 2020 have a width and/or pitch comparable to features of the device. For example, structure 2010 has a width and/or pitch comparable to features of a corresponding device structure created in a first patterning process. Similarly, for example structure 2020 has a width and/or pitch comparable to a feature of a corresponding device structure created in the second patterning process.

In unit cell 2000, the feature that will break the symmetry of the different physical configurations of structures within unit cell 2000 is the physical difference between structure 2010 and structure 2020. In one embodiment, this difference is the difference in widths of structures 2010 and 2020 in the X-direction as schematically shown in FIG. 21A. In one embodiment, this difference is a difference in the material composition of structures 2010 and 2020, for example structure 2010 is made of a different material than structure 2020. In one embodiment, there may be a combination of physical differences, for example differences in width and physical composition.

The result of the physical difference that exists in the case of the unit cell 2000 is that a relative shift 2040 in the X-direction in the XY plane between the structures 2010 and 2020 causes asymmetry in the unit cell 2000. . This is shown in Fig. 21B. In FIG. 21B, the structure 2010 is shifted from its nominal (eg, design) position of the structure 2010 shown in FIG. 21A once it is created in the second patterning process. As a result, a displacement 2050 from the anchor 2030 occurs. Thus, assuming that the unit cell 2000 corresponds to a situation where no overlay exists, the displacement 2050 preferably processes radiation redirected by the target including the unit cell 2000 as described above (e.g. For example, weight and pupil distribution).

Since the unit cell 2000 exhibits asymmetry with respect to the Y axis, if the translation in the X-direction is combined with the feature that causes the asymmetry (here the physical difference between the structures 2010 and 2020), then X- A radiation distribution is provided from which the overlay value can be determined. In one embodiment, such an X-overlay value will correspond to an X-overlay of a feature of the device manufactured using each patterning process. Now, of course, the unit cell 2000 can be rotated substantially 90 degrees about the anchor 2030 to provide a Y-overlay value for the relative shift in the Y-direction between the structures 2010 and 2020. In one embodiment, such a Y-overlay value will correspond to the Y-overlay of a feature of the device fabricated using each patterning process. In one embodiment, in such a case, the device features corresponding to structures 2010 and 2020 will extend in the X-direction.

Therefore, in one embodiment, the structures 2010 and 2020 of the unit cell correspond to respective features of the device extending in the same direction. As a result, the structure of the unit cell 2000 will provide the value of the overlay in a direction orthogonal to the direction of extension/elongation of the features of the device. Thus, by identifying a device feature extending in the same direction for which the overlay in the orthogonal direction thereto is of interest, the unit cell 2000 properly selects the structures 2010 and 2020 and the structures are It can be designed to mimic this overlay by allowing it to be created.

In Fig. 21, the unit cell 2000 is designed to primarily determine the overlay between the structures (eg, lines) themselves being formed. In some patterning processes, a specific pattern is transferred to a substrate having a structure, causing a portion of the structure to be removed when etching is performed in relation to the pattern. This process and its results will be referred to herein as cuts. For example, a device structure (eg, a line) may be cut into a plurality of pieces and/or an end of the device structure may be cut away. As can be appreciated, it may be desirable to know whether the cuts have been manufactured correctly. Thus, it may be desirable to know the overlay between the cuts and/or the overlay between the cuts and the structure.

Moreover, the unit cell of FIG. 21 makes it possible to determine the value of the overlay in a direction orthogonal to the direction of extension/elongation of a feature of the device. However, it may be desirable to determine the overlay in a direction parallel to the direction of extension/elongation of the features of the device.

Referring now to FIG. 22, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weight and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 22A, an example of a unit cell 2100 is shown. The unit cell 2100 includes a structure 2110 (a plurality of lines 2110 in this case) and a structure 2120 (a second plurality of lines 2120 in this case). As described in more detail below, overlays in X and Y can be determined from this non-product target design in this embodiment.

In this embodiment, the unit cell 2100 has the features of the unit cell 2000 of FIG. 21, so that the structure 2110 is created in the first patterning process and the structure 2120 is created in the second patterning process. If there is a physical difference between the structures 2110 and 2120, the X-direction overlay may be determined as described above. However, for example, if an X-direction overlay is not desired, the structures 2110 and 2120 may be created in the same patterning process and/or the structures 2110 and 2120 may have the same physical properties, i.e., the physical difference. Does not have However, even if an X-direction overlay is not desired, structures 2110 and 2120 may have different physical properties to provide better measurement signals.

Therefore, in this embodiment, which allows determining the overlay at X and Y, the unit cell 2100 includes a structure 2110 created in a first patterning process and a structure 2120 created in a second patterning process. . The anchor 2130 is marked to show the symmetry of the unit cell. In this case, the unit cell 2100 has symmetry in the Y direction and symmetry in the X direction. 22A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

In one embodiment, structure 2110 corresponds to a feature of a device manufactured using a first patterning process as described above, and structure 2120 corresponds to a feature of a device manufactured using a second patterning process. . And, in the unit cell 2100, the feature that will break the symmetry for the different physical configurations of the structures in the unit cell 2100 is the physical difference between the structure 2110 and the structure 2120. In one embodiment, this difference is the difference in the widths of structures 2110 and 2120 in the X-direction as schematically shown in FIG. 22A. In one embodiment, this difference is a difference in the material composition of structures 2110 and 2120, for example, structure 2110 is made of a different material than structure 2120.

As discussed above, the result of the physical difference present in the case of the unit cell 2100 is that a relative shift 2180 in the X-direction in the XY plane between the structures 2110 and 2120 results in the unit cell 2100 It is that asymmetry is caused within. This is shown in Fig. 22C. In FIG. 22C, the structure 2110 is shifted from its nominal (eg, design) position of the structure 2110 shown in FIG. 22A once it is created in the second patterning process. The result is a displacement 2190 from the anchor 2130. Thus, assuming that the unit cell 2100 corresponds to a situation in which no overlay exists, the displacement 2190 preferably processes radiation redirected by the target comprising the unit cell 2100 as described above (e.g. For example, weights and pupil distribution).

Since the unit cell 2100 exhibits an asymmetry with respect to the Y axis, if the translation in the X-direction is combined with the feature that causes the asymmetry (here the physical difference between the structures 2110 and 2120), the X- A radiation distribution is provided from which the overlay value can be determined. In one embodiment, such an X-overlay value will correspond to an X-overlay of a feature of the device manufactured using each patterning process. Now, of course, unit cell 2100 can be rotated substantially 90 degrees about anchor 2130 to provide a Y-overlay value for the relative shift in the Y-direction between structures 2110 and 2120. In one embodiment, such a Y-overlay value will correspond to the Y-overlay of a feature of the device fabricated using each patterning process. In one embodiment, in such a case, device features corresponding to structures 2110 and 2120 will extend in the X-direction.

Now, the unit cell 2100 also enables determination of the overlay in the Y direction. Similar to how a structure in a unit cell of a non-product target can correspond to a feature in a device, a cut in a non-product target design can correspond to a feature (eg, a cut) in the device.

Referring to FIG. 22A, the unit cell 2100 includes a cutting portion 2150 generated in a first patterning process and a cutting portion 2140 generated in a second patterning process. The cutouts 2150 and 2140 are arranged to remain symmetric to the unit cells within their nominal physical configuration.

In one embodiment, the cutout 2150 corresponds to a feature of the device fabricated using the first patterning process. That is, the cutout 2150 will be created by a first patterning process that creates a corresponding device feature of the device. For example, the creation of cutout 2150 corresponds to a comparable production of cutouts in the device. Similarly, in one embodiment, the cutout 2140 corresponds to a feature of the device manufactured by the second patterning process. That is, the cutout 2140 will be created by a second patterning process that creates a corresponding device feature of the device. For example, the creation of a cutout 2140 corresponds to a comparable production of a cutout in the device. Thus, in one embodiment, the cutout 2150 corresponds to one or more features (eg, one or more cutouts) of the device extending in a direction essentially parallel to, for example, the cutout 2150. Similarly, in one embodiment, the cutout 2140 corresponds to one or more features of the device (e.g., one or more cutouts) extending in a direction essentially parallel to the cutout 2140, for example. do. In one embodiment, the cutting portion 2150 is created on a different layer than the cutting portion 2140. Therefore, in one embodiment, cutouts 2150 and 2140 may be used to determine the overlay of corresponding cutouts in the device in the Y-direction.

In one embodiment, cutouts 2150 and 2140 have a width and/or pitch comparable to features of the device. For example, the cutout 2150 has a width and/or a pitch comparable to a feature (eg, one or more cutouts) of a corresponding device structure created in the first patterning process. Similarly, for example cutouts 2140 have a width and/or pitch comparable to a feature (eg, one or more cutouts) of a corresponding device structure created in the second patterning process.

In the unit cell 2100, the features that will cause the symmetry to break with respect to the different physical configurations of the structures in the unit cell 2100 are the cutouts 2150 and 2140 that will create asymmetry upon a relative shift between the cutouts 2150 and 2140. ). In one embodiment, cutouts 2140 are created within each structure 2120, while cutouts 2150 are not created within each structure 2110. As can be appreciated, cutouts 2150 may be created within each structure 2110, while cutouts 2140 are not created within each structure 2120. As can be appreciated, many different variations are possible with respect to the cut, including different positions of the cut and/or different sizes of the cut.

The result of this arrangement of the cutting portions 2150 and 2140 is that a relative shift 2160 in the Y-direction in the X-Y plane between the cutting portions 2150 and 2140 causes asymmetry in the unit cell 2100. This is shown in Fig. 22B. In Fig. 22B, the cutout 2150 is shifted from its nominal (e.g., design) position shown in Fig. 22A when created in the first patterning process. The result is a displacement 2170 from the anchor 2130. Thus, assuming that the unit cell 2100 corresponds to a situation where no overlay exists, the displacement 2170 preferably processes radiation redirected by the target comprising the unit cell 2100 as described above (e.g. For example, weight and pupil distribution).

Since the unit cell 2100 exhibits asymmetry with respect to the X axis, when the translation in the Y-direction is combined with a feature that causes the asymmetry (here, the arrangement of the cutouts 2140 and 2150), the Y-overlay from it The radiation distribution from which the value can be determined is provided. In one embodiment, such a Y-overlay value will correspond to the Y-overlay of a feature of the device fabricated using each patterning process. Now, of course, the unit cell 2100 can be rotated substantially 90 degrees about the anchor 2130 to provide an X-overlay value for the relative shift in the X-direction between the cuts 2140 and 2150. In one embodiment, such an X-overlay value will correspond to an X-overlay of a feature (eg, cut) of a device manufactured using each patterning process. In one embodiment, in such a case, device features (eg, cutouts) corresponding to cutouts 2140 and 2150 will extend in the X-direction.

Therefore, in one embodiment, the cutouts 2140 and 2150 of the unit cell correspond to respective features of the device extending in the same direction. As a result, the structure of the unit cell 2100 will provide the value of the overlay in a direction parallel to the direction of extension/elongation of a feature of the device. Thus, by identifying a device feature extending in the same direction, for which the overlay in a direction parallel to it is of interest, the unit cell 2100 properly selects the cutouts 2140 and 2150, and when the device feature is created, the structure Can be designed to mimic this overlay by having them created.

As mentioned above, in one embodiment, cuts 2140 and 2150 may be created within structures 2110 and 2120 in a manner similar to that cuts are manufactured within device features. Thus, the cutouts 2140 and 2150 can provide a good measure of the cutout overlay created when creating the device structure. However, in one embodiment, cutouts 2140 and 2150 may instead be voids created when structures 2110 and 2120 are created, and will be created as part of the corresponding patterning process to create the structure of the device. I can. Thus, voids 2140 and 2150 in this case can provide a good measure of the overlay of the structure created when manufacturing the device.

And, although FIG. 22 shows cuts/voids that allow determination of the overlay, structures 2110 and 2120 may have one or more protrusions or variations, for example protrusions at the location of the cuts shown. Hence, the relative displacement between these protrusions or deformations can cause asymmetry in the unit cell, such as cutouts 2140 and 2150. The protrusions or deformations may be created when structures 2110 and 2120 are created or may be created by a cutting process. Thus, protrusions or deformations may be, for example, between device structures (e.g., in the case of protrusions or deformations that occurred when structures 2110 and 2120 were created) or between device cuts (e.g., structures 2110 And in the case of protrusions or deformations resulting from cutting 2120).

22D schematically shows a non-product target comprising a plurality of instances of a unit cell. In this non-limiting example, FIG. 22D includes at least 4 instances of unit cells. 22D shows an instance of a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay). In one embodiment, the pitch 2192 of the structure 2110 is compared to the pitch 2194 of the structure 2120.

In FIG. 22D, if, for example, the second patterning process is not well aligned in the X-direction so that there is a relative shift between the structures 2110 and 2120, the Y-symmetry is broken and the Y-symmetry in the pupil is also broken. Thus, the measurement of the target in such conditions can be converted to an X-overlay determination. Consequently, structures 2110 and 2120 are used to determine the X-overlay. Similarly, if, for example, the second patterning process is not well aligned in the Y-direction so that there is a relative shift between the cuts 2140 and 2150, the X-symmetry is broken and the X-symmetry in the pupil is also broken. Thus, the measurement of the target in such conditions can be turned into a Y-overlay determination. Consequently, cutouts 2140 and 2150 are used to determine the Y-overlay. Further, as can be seen in Fig. 22D, the shift of the cutting portion in the Y direction does not change the symmetry about the Y axis, and the shift of the structure in the X direction does not change the symmetry about the X axis. Thus, the X and Y direction overlays are decoupled. Hence, a poorly aligned patterning process in the X- and Y- directions breaks the X- and Y-symmetry, while different overlays can be separated from the signal in question.

In one embodiment, the number of structures and their size, pitch, etc. may be configured to be nearly comparable to the patterning process of the device pattern. Similarly, the number of cuts (or protrusions/deformations) and their size, pitch, etc. can be configured to be nearly comparable to the patterning process of the device pattern. For example, the cut will be compared to the CD and pitch used in the device, if possible. However, in one embodiment, the location and/or number of cuts are adapted to produce a symmetrical unit cell. Furthermore, the non-product target overlay sensitivity can be adjusted by adjusting the pitch of the structure and cut (or protrusion/deformation).

Referring to FIG. 23, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 23A, an example of a unit cell 2300 is shown. The unit cell 2300 includes a structure 2310 (a plurality of lines 2310 in this case) and a structure 2320 (a second plurality of lines 2320 in this case). Unlike FIGS. 21 and 22, the structure 2310 extends in a direction substantially perpendicular to the structure 2320. Anchors 2340 are marked to show the symmetry of the unit cells. In this case, the unit cell 2300 has symmetry in the Y direction. 23A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

Therefore, in this embodiment of the unit cell 2300, the overlay in the X-direction between the structure extending in the first direction and the cutout or structure extending in a second direction essentially orthogonal to the first direction is It can be determined from radiation redirected from the cell.

In particular, similar to the principles described above, the unit cell 2300 includes a structure 2310 created in a first patterning process and a cutout 2330 and/or a structure 2320 created in a second patterning process. For example, if an overlay between the structure 2310 and the cutout 2330 is desired, the structure 2310 is created in a first patterning process and the cutout 2330 is created in a second patterning process (or (2320) is also created in the second patterning process). For example, if an overlay between the structures 2310 and 2320 is desired, then the structure 2310 is created in a first patterning process and the structure 2320 has voids comparable to, for example, the cutout 2330. And is created in a second patterning process. Structures 2310 and 2320 and cutouts 2330 are arranged to remain symmetric to the unit cells within their nominal physical configuration.

Similar to the embodiment described above, the structure 2310 corresponds to a feature of the device fabricated using the first patterning process. That is, the structure 2310 will be created by a first patterning process that creates a corresponding device feature of the device. For example, the creation of structure 2310 corresponds to a comparable creation of a structure in the device. Similarly, in one embodiment, structure 2320 and/or cutout 2330 correspond to features of the device fabricated by the second patterning process. That is, the structure 2320 and/or the cutout 2330 will be created by a second patterning process that creates a corresponding device feature of the device. For example, the creation of cutout 2330 corresponds to a comparable production of cutouts in the device. Thus, in one embodiment, structure 2310 corresponds to one or more features (eg, one or more structures) of the device extending in a direction essentially parallel to structure 2310, for example. Similarly, structures 2320 and/or cutouts 2330 correspond to one or more features of the device extending in a second direction essentially perpendicular to the first direction, for example. In one embodiment, structure 2320 and/or cutout 2330 are created on a different layer than structure 2310. Thus, in one embodiment, the cutout 2330 (or voids comparable to the cutout of the structure 2320) may be used to determine the X-direction overlay of the corresponding feature in the device.

In one embodiment, structure 2310 and structure 2320 and/or cutout 2330 have a width and/or pitch comparable to features of the device. For example, the structure 2310 has a width and/or pitch that is comparable to a feature (eg, one or more structures) of a corresponding device structure created in the first patterning process. Similarly, structures 2320 and/or cutouts 2330, for example, have a width and/or pitch comparable to features of a corresponding device structure created in the second patterning process.

In the unit cell 2300, the feature that will cause the symmetry to be broken for different physical configurations of the structures in the unit cell 2300 is between the structure 2310 and the cuts 2330 (or between the structures 2310 and 2320). It is the arrangement of the cuts 2330 (or comparable voids in the structure 2320) that will create asymmetry upon relative shift. As can be understood, different positions of cuts/voids and/or different positions of cuts/voids Many different variations are possible with respect to cuts/voids, including size.

The result of arranging the cutting portion 2330 (or void 2330) in combination with the essentially vertical structures 2310 and 2320 is between the structure 2310 and the cutting portion 2330 (or a structure in which voids exist). The relative shift 2350 in the X-direction in the XY plane (between 2310 and 2320) causes an asymmetry in the unit cell 2300. This is shown in Fig. 23B. In Fig. 23B, the cutout 2330 is shifted from its nominal (e.g., design) position shown in Fig. 23A when created in the second patterning process. As a result, a displacement 2360 from the anchor 2340 occurs. Thus, assuming that the unit cell 2300 corresponds to a situation in which no overlay exists, the displacement 2360 preferably processes radiation redirected by the target comprising the unit cell 2300 as described above (e.g. For example, weight and pupil distribution).

Since the unit cell 2300 exhibits asymmetry with respect to the Y axis, the translation in the X-direction causes the asymmetry (here, the cutout 2330 in combination with the essentially perpendicular structures 2310 and 2320). When combined with (or the arrangement of the voids 2330), a radiation distribution from which an X-overlay value can be determined is provided. In one embodiment, such an X-overlay value will correspond to an X-overlay of a feature of the device manufactured using each patterning process.

Therefore, in one embodiment, the structure 2310 and the structure 2320 and/or the cutout 2330 of the unit cell correspond to each feature of the device extending in the same direction. As a result, the structure of the unit cell 2300 may extend in a vertical direction or provide an overlay value for an elongated feature. Thus, by identifying a device feature extending in an orthogonal direction for which the overlay in a particular direction thereon is of interest, the unit cell 2300 can be configured with the cutout 2330 (or voids) in relation to the orthogonal structures 2310 and 2320. 2330)) and device features can be designed to mimic these overlays by having them created as they are created.

And, while FIG. 23 shows cuts/voids that enable determination of the overlay, structures 2310 and 2320 may have one or more protrusions or variations, for example protrusions at the location of the cuts shown. Therefore, the relative displacement between these protrusions or deformations may cause asymmetry in the unit cell, such as the cutout 2330. The protrusions or deformations may be created when structures 2310 and 2320 are created or may be created by a cutting process. Thus, protrusions or deformations enable determination of an overlay between, for example, device structures (e.g., in the case of protrusions or deformations that occurred when structures 2310 and 2320 were created) or between cuts and structures. Can be used to

Now, of course, the unit cell 2300 is rotated substantially 90 degrees about the anchor 2340 so that the relative shift in the Y-direction between the structure 2310 and the structure 2320 and/or the cutout 2330 is Y-overlay value can be provided. In one embodiment, such a Y-overlay value will correspond to the Y-overlay of a feature of the device fabricated using each patterning process.

Referring to FIG. 24, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 24A, an example of a unit cell 2400 is shown. The unit cell 2400 includes a structure 2410 (a plurality of lines 2410 in this case) and a structure 2420 (a second plurality of lines 2420 in this case). The structure 2410 extends in a direction substantially perpendicular to the structure 2420. Anchor 2440 is marked to show the symmetry of the unit cell. In this case, the unit cell 2400 has symmetry in the X direction. 24A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

Therefore, in this embodiment of the unit cell 2400, the overlay in the Y-direction between the structure extending in the first direction and the cutout or structure extending in a second direction essentially orthogonal to the first direction is It can be determined from radiation redirected from the cell.

Fig. 24 is a substantially inverted arrangement of Fig. 23; While Fig. 23 is designed to determine the X-direction overlay, Fig. 24 is also designed to determine the Y-direction overlay; However, similar to FIG. 23, the unit cell of FIG. 24 can be rotated 90 degrees to determine the X-direction overlay. However, unlike FIG. 23, the cut 2430 (or void 2430 of the resulting structure 2410) is created in the first patterning process as compared to the second patterning process in the embodiment of FIG. 24.

Therefore, in the unit cell 2400, the feature that will cause the symmetry to break with respect to the different physical configurations of the structures in the unit cell 2400 is between the cutout 2430 and the structure 2420 (or between the structures 2410 and 2420). ) Is the arrangement of the cutouts 2430 (or comparable voids in the structure 2410) that will create an asymmetry upon a relative shift of the. Many different variations are possible with respect to cuts/voids, including different sizes of.

The result of arranging the cutting portion 2430 (or void 2430) in combination with the essentially vertical structures 2410 and 2420 is between the cutting portion 2430 and the structure 2420 (or a structure in which voids exist). The relative shift 2450 in the Y-direction in the XY plane (between 2410 and 2420) causes an asymmetry in the unit cell 2400. This is shown in Fig. 24B. In Fig. 24B, the cutout 2430 is shifted from its nominal (e.g., design) position shown in Fig. 24A once it is created in the first patterning process. The result is a displacement 2460 from the anchor 2440. Thus, assuming that the unit cell 2300 corresponds to a situation in which no overlay exists, the displacement 2460 preferably processes radiation redirected by the target comprising the unit cell 2400 as described above (e.g. For example, weight and pupil distribution).

Since the unit cell 2400 exhibits asymmetry with respect to the X axis, the translation in the Y-direction causes the asymmetry (here the cutout 2430 in combination with the essentially perpendicular structures 2410 and 2420). When combined with (or the arrangement of voids 2430), a radiation distribution from which the Y-overlay value can be determined is provided. In one embodiment, such a Y-overlay value will correspond to the Y-overlay of a feature of the device fabricated using each patterning process.

And, while FIG. 24 shows cuts/voids that enable determination of the overlay, structures 2410 and 2420 may have one or more protrusions or variations, for example protrusions at the location of the cuts shown. Hence, the relative displacement between these protrusions or deformations can cause asymmetry in the unit cell, such as the cutout 2430. The protrusions or deformations may be created when structures 2410 and 2420 are created or may be created by a cutting process. Thus, the protrusions or deformations enable determination of, for example, an overlay between device structures (e.g., in the case of protrusions or deformations that occurred when structures 2410 and 2420 were created) or between cuts and structures. Can be used to

Now, of course, the unit cell 2400 is rotated substantially 90 degrees about the anchor 2440 to the relative shift in the X-direction between the structure 2410 and/or the cutout 2430 and the structure 2420. You can provide an X-overlay value. In one embodiment, such an X-overlay value will correspond to an X-overlay of a feature of the device manufactured using each patterning process.

Referring to FIG. 25, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 25A, an example of a unit cell 2500 is shown. The unit cell 2500 includes a structure 2510 generated in a first patterning process (a plurality of lines 2510 in this case) and a structure 2520 generated in a second patterning process (in this case, a second plurality of lines ( 2520)). The structure 2510 extends in a direction substantially parallel to the structure 2520. The anchor 2530 is marked to show the symmetry of the unit cell. In this case, the unit cell 2500 has symmetry in the Y direction. FIG. 25A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

The non-product target design of FIG. 25 is compared to the non-product target design of FIG. 21. The difference is that the center line 2510 is not provided as compared to the center line 2010 provided in FIG. 20. This means that the unit cell 2500 and the non-product target involve less structure than FIG. 20, and thus, for example, the related modeling can be improved. However, this may involve a pitch between lines other than the corresponding feature in the device, for example the pitch for the lines of structure 2520 may need to be different from the pitch of comparable lines in the device.

In one embodiment, structure 2510 includes at least two sub-structures (eg, pre-like structures). Alternatively or additionally, structure 2520 includes at least two sub-structures (eg, pre-like structures). This is to enable enough signals. This principle can also be applied to other embodiments described herein.

Similar to FIG. 21, the feature that breaks the symmetry is the physical difference between structures 2510 and 2520, which in the illustrated embodiment is the difference in width of structures 2510 and 2520. Therefore, similar to FIG. 21 and as shown in FIG. 25B, the relative shift 2540 between structures 2510 and 2520 causes the symmetry in the Y-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2550 to be determined. The relative displacement 2550 may correspond to an X-direction overlay of a corresponding device feature.

Referring to FIG. 26, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weight and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 26A, an example of a unit cell 2600 is shown. The unit cell 2600 includes a structure 2610 created in a first patterning process (a plurality of lines 2610 in this case) and a structure 2620 created in a second patterning process (in this case, a second plurality of lines ( 2620)). The structure 2610 extends in a direction substantially parallel to the structure 2620. Further, the structure 2610 includes a cut portion 2630 produced by the patterning process and the structure 2620 includes a cut portion 2640 produced by the patterning process. Anchor 2650 is marked to show the symmetry of the unit cell. In this case, the unit cell 2600 has symmetry in the Y direction and symmetry in the X direction. 26A shows a unit cell in a symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

The non-product target design of FIG. 26 is compared to the non-product target design of FIG. 22 in that it can be used in layout and to determine the overlay in the X and Y directions. The difference is that the center line 2610 is not provided as compared to the center line 2010 provided in FIG. 20. This means that the unit cell 2600 and the non-product target involve less structure than FIG. 20, and thus, for example, the related modeling can be improved. Further, the cutting portions 2630 and 2640 have an arrangement configuration different from that of FIG. 22. The arrangement of the cutting portions provides asymmetry, but is also intended to cause the symmetry to be broken if there is a relative shift accompanying the cutting portions.

As a result of this different arrangement of Figure 26, this design may involve a pitch between lines other than the corresponding feature in the device, e.g. the pitch for the lines of structure 2620 is comparable to the lines in the device. It may need to be different from the pitch of.

Similar to FIG. 22, the feature that breaks the symmetry is the physical difference between structures 2610 and 2620, which is the difference in widths of structures 2610 and 2620 in the illustrated embodiment. Therefore, as similar to FIG. 22 and shown in FIG. 26C, the relative shift 2670 between structures 2610 and 2620 causes the symmetry in the Y-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2680 to be determined. The relative displacement 2680 may correspond to an X-direction overlay of a corresponding device feature.

Furthermore, similar to FIG. 22, the feature that causes the symmetry to break is the arrangement of the cutting portions 2630 and 2640. Therefore, similar to FIG. 22 and as shown in FIG. 26B, the relative shift 2650 between the cuts 2630 and 2640 causes the symmetry in the X-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2660 to be determined. The relative displacement 2660 may correspond to the Y-direction overlay of the corresponding device feature.

Referring to FIG. 27, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 27A, an example of a unit cell 2700 is shown. The unit cell 2700 is a structure 2710 created in a first patterning process (in this case, a plurality of lines 2710), a structure 2720 created in a second patterning process (in this case, a second plurality of Line 2720 ), and a structure 2730 created in a third patterning process (in this case, a third plurality of lines 2730 ). The structure 2710 extends in a direction substantially parallel to the structure 2720. Further, the structure 2730 extends in a direction substantially perpendicular to the structures 2710 and 2720. Further, the structure 2710 includes a cut portion 2740 produced by the patterning process and a cut portion 2750 produced by the patterning process. Anchor 2750 is marked to show the symmetry of the unit cell. In this case, the unit cell 2700 has symmetry in the Y direction and symmetry in the X direction. Figure 27A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

The non-product target design of FIG. 27 is compared to the non-product target design of FIG. 22 in that it can be used in layout and to determine the overlay in the X and Y directions. The difference is that additional structures 2730 are provided for the third patterning process.

Because of this arrangement, such a non-product target may, for example, make it possible to determine an overlay between features across three or more layers of the device; For example, such a non-product target may be an overlay between a feature in a first layer of the device and a feature in a second layer of the device and an overlay between a feature in the first layer of the device and a feature in a third layer of the device. It may make it possible to determine the overlay.

For example, as described with respect to FIG. 22, a shift in the X direction of structures 2710 and 2720 may enable determination of an X-direction overlay between device features corresponding to structures 2710 and 2720. have.

However, in addition to the arrangement of FIG. 22, the shift in the Y direction between the cutting portion 2750 and the structure 2730 creates a Y direction overlay between the cutting portion 2750 and the device features corresponding to the structure 2730. It can make it possible to decide. And, in this embodiment, the structure 2730 may be on a different layer from the structures 2710 and 2720.

A feature that breaks symmetry with respect to the structure 2730 is the arrangement of the structure 2730 and the relative cutout 2750. Therefore, as shown in Fig. 27B, the relative shift 2760 between the structure 2730 and the cutting portion 2750 causes the symmetry in the X-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2770 to be determined. The relative displacement 2670 may correspond to the Y direction overlay of the corresponding device feature.

Thus, Fig. 27 shows a combined target that allows the measurement of the overlay between three different process steps. The target enables, for example, layer 1 feature-layer 2 feature overlay measurements (X direction) and layer 1 feature-layer 3 feature overlay measurements (Y-direction). Of course, in one embodiment, the target of FIG. 27 is a discrete target (e.g., a target and a first layer feature with structures 2710 and 2720 and cutouts 2740 for measuring a layer 1 feature-2 layer feature overlay). It is separated into structures 2710 and 2730 for measuring the three-layer feature overlay and another target having a cutting portion 2740), so that one target can be provided for each pair of layers, rather than a combined target as shown in FIG. 27. have.

Referring to FIG. 28, a non-limiting example of a unit cell of a non-product target design is shown to determine patterning process parameters (eg, weights and pupil distribution) using the techniques described herein. In this case, the unit cell is for determining the overlay. In FIG. 28A, an example of a unit cell 2800 is shown. The unit cell 2800 includes a structure 2810 created in a first patterning process (in this case, a plurality of closed curves 2810, e.g., essentially circles or ellipses) and a structure 2820 created in a second patterning process. (In this case, a plurality of closed curves 2820, for example essentially circles or ellipses) are included. The structure 2810 extends in a direction substantially parallel to the structure 2820. In this case, the unit cell 2800 has symmetry in the Y direction and symmetry in the X direction. 28A shows a unit cell in symmetrical shape and will correspond to a specific nominal overlay value (eg, zero overlay).

In this arrangement, as shown in Fig. 28B, the relative shift 2830 between the structures 2810 and 2820 causes the symmetry in the Y-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2840 to be determined. The relative displacement 2840 may correspond to an X-direction overlay of a corresponding device feature.

Further, in this arrangement, as shown in Fig. 28C, the relative shift 2850 between the structures 2810 and 2820 causes the symmetry in the X-direction to be broken. Breaking the symmetry results in a specific radiation distribution that allows the relative displacement 2860 to be determined. The relative displacement 2860 may correspond to the Y-direction overlay of the corresponding device feature.

A feature that breaks the symmetry of the structure is the staggered configuration of the structure 2810 relative to the structure 2820. In this embodiment, the structure 2810 is shown to have a different width than the structure 2820, but it is not necessary to have this difference if the structures 2810 and 2820 are in a staggered arrangement as shown. Otherwise, if structures 2810 and 2820 are not staggered, physical differences (eg, different widths, different materials, etc.) can be used to break the symmetry.

Different combinations of features in Figs. Makes it possible to do. In one embodiment, separate targets may each be created for a single type of parameter (e.g., a target for an X-direction overlay and a separate target for a Y-direction overlay, an overlay between first combinations of features). A separate target for the overlay between the target for and the second combinations of features, etc.) or multiple targets may be created to determine the combination of types of parameters.

Referring now to FIG. 29, FIG. 29A schematically illustrates an example of a device pattern feature. For example, the device pattern feature may be for a memory device (eg SRAM). As can be appreciated, a full memory device may have even more features within the illustrated area. However, it may be desirable to determine the overlay of a particular combination of device pattern features shown in FIG. 29A. Such an overlay can be used for patterning process control, defect prediction in the patterning process, and the like, as discussed in more detail herein.

In FIG. 29A, the device pattern includes a plurality of line features 2900 extending substantially parallel to each other. Furthermore, the device pattern includes a plurality of line features 2910 extending substantially parallel to each other and interleaving with the line features 2900. In one exemplary embodiment of the multi-patterning process, which will be described hereinafter, feature 2900 is created first, followed by feature 2910 due to, for example, resolution limitations.

Furthermore, it is desirable to have multiple segments alongside, for example, line features 2900. Therefore, in a multi-patterning process, these segments can be created by the cutting portions as described above. Therefore, the device pattern includes a plurality of cutout features 2920 for line features 2900. Furthermore, the device pattern includes a plurality of cutout features 2930 for line features 2910.

Then, device pattern features may be created by a plurality of litho-etching (LE) processes. 29B, 29C, 29D and 29E schematically illustrate an example of steps in a device multi-patterning method. In FIG. 29B, a plurality of line features 2900 are created. Then, in FIG. 29C, cut 2920 is applied to feature 2900, resulting in segmented line feature 2900 as shown in FIG. 29A.

In FIG. 29D, a plurality of line features 2910 are created, wherein the plurality of line features 2910 are created in an interleaved manner between the line features 2900. Then, in Fig. 29E, a cutout 2930 is applied to the feature 2910, resulting in a segmented line feature 2910 as shown in Fig. 29A.

Thus, it may be desirable to determine the overlay between the creations of the cut 2920 and the cut 2930. Alternatively, it may be desirable to determine an overlay between structures 2900 and 2910. Therefore, as can be appreciated, there may be a variety of different overlays that may preferably be determined and then monitored, controlled, etc.

Therefore, the layers of interest are identified, and the overlay to be determined (eg, an overlay in the X-direction, an overlay in the Y direction, or an overlay in both X and Y directions) is identified. In this example, it may be desirable to determine an X-direction overlay between structures 2900 and 2910 and a Y-direction overlay between cutouts 2920 and 2930.

Therefore, having one or more specific overlays of interest within the device can be designed to help non-product targets determine the overlay. In the case of the device feature of FIG. 29A, the line space pattern of the structure can be created with a pitch and CD comparable to the layer of interest. An example of such a structure of a non-product target design is schematically shown in FIG. 29F. In this case, for example, structure 2940 would be created in the same patterning process as structure 2900 was created, and structure 2950 would be created in the same patterning process as structure 2910. As described above with respect to FIGS. 21 to 28, when the structures 2940 and 2950 are created to cause the symmetry to be broken, a physical difference between the structures 2940 and 2950 is required to enable the X-direction overlay determination. May be provided to enable a relative shift in the X direction. Since structures 2940 and 2950 substantially serve as proxies for structures 2900 and 2910, the relative X direction between the structures 2940 and 2950 from radiation redirected by the non-product target in that condition. Determining the displacement may correspond to an X-direction overlay for structures 2900 and 2910.

Further, referring to FIG. 29G, one or more cuts are introduced into the structure of the non-product target design of FIG. 29F to enable determination of the Y direction overlay. To make this possible, a unit cell 2960 is defined. As shown, the unit cell has structures 2940 and 2950, and has a Y symmetry broken by the relative displacement of the structures 2940 and 2950 in the X direction. Therefore, in order to enable the Y direction overlay determination, a feature is introduced when there is a relative displacement in the Y direction to create an asymmetry in the X direction. As mentioned above, it is desired to determine the overlay in the Y direction between the cuts 2920 and 2930. Therefore, since the cutting portions 2920 and 2930 remove portions of the structures 2900 and 2910, respectively, comparable cutting portions are introduced into the structures 2940 and 2950, respectively. In this embodiment, such cuts are cuts 2970 and 2980. The cutouts 2970 and 2980 create a reference for determining the Y-direction overlay due to the relative shift between them while the cutouts 2970 and 2980 are being created. Since the cutouts 2970 and 2980 substantially serve as a proxy for the cutouts 2920 and 2930, the Y between cutouts 2970 and 2980 from radiation redirected by the non-product target in that condition. Determining the relative displacement in the direction may correspond to the Y-direction overlay on the cutting portions 2920 and 2930.

In one embodiment, cutouts 2970 and 2980 cause the unit cells to be symmetrical in the X direction in their nominal configuration. Furthermore, in one embodiment, the cutout does not affect the symmetry of the unit cell in terms of the X overlay determination as described above. In one embodiment, cutouts 2970 and 2980 have a CD and pitch comparable to cutouts in the device patterning process, if possible. However, the size, number and location of the cuts can be adapted to create a symmetrical unit cell. In one embodiment, as shown in FIG. 29G, the unit cell is repeated as a plurality of instances to form a non-product target to be created on the substrate.

Therefore, in this embodiment, in the nominal configuration, the unit cell 2960 has both X and Y symmetry. Furthermore, if there is a relative shift in the Y direction between features, the X symmetry within the unit cell is broken (while the Y symmetry is preserved), so that the Y direction overlay can be determined. Also, if there is a relative shift in the X direction between features, the Y symmetry within the unit cell is broken (whereas X symmetry is preserved), so that the X direction overlay can be determined.

Referring now to FIG. 30, FIG. 30A schematically illustrates another example of a device pattern feature. For example, the device pattern feature may be for a memory device (eg SRAM). As can be appreciated, a full memory device may have even more features within the illustrated area. However, it may be desirable to determine the overlay of a particular combination of device pattern features shown in FIG. 30A. Such an overlay can be used for patterning process control, defect prediction in the patterning process, and the like, as discussed in more detail herein.

In Fig. 30A, the device pattern includes a plurality of line features 3000 extending substantially parallel to each other. Furthermore, the device pattern includes a plurality of line features 3010 that are substantially parallel to each other and extend substantially perpendicular to the feature 3000. In one exemplary embodiment of the multi-patterning process to be described hereinafter, feature 3010 is first created, and then feature 3000 is created.

Furthermore, it is desirable to have multiple segments alongside, for example, line features 3000. Therefore, in a multi-patterning process, these segments can be created by the cutting portions as described above. Therefore, the device pattern includes a plurality of cutout features 3020 for line features 3000. The device pattern features can then be created by a plurality of litho-etch (LE) processes different or similar to those described with respect to FIGS. 29B-29E.

Thus, it may be desirable to determine the overlay between structures 3000 and 3010. Alternatively, it may be desirable to determine the overlay between the creations of the cut 3020 and the structure 3010. Therefore, as can be appreciated, there may be a variety of different overlays that may preferably be determined and then monitored, controlled, etc.

Therefore, the layers of interest are identified, and the overlay to be determined (eg, an overlay in the X-direction, an overlay in the Y direction, or an overlay in both X and Y directions) is identified. In this example, it may be desirable to determine the Y-direction overlay between the structure 3010 and the cut 3020.

Therefore, having one or more specific overlays of interest within the device can be designed to help non-product targets determine the overlay. In the case of the device feature of Fig. 30A, the line space pattern of the structure can be created with a pitch and CD comparable to the layer of interest. An example of such a structure of a non-product target design is schematically shown in FIG. 30C. In this case, for example, the structure 3040 will be created in the same patterning process as the structure 3010 was created, and the structure 3030 will be created in the same patterning process as the structure 3000. As discussed above with respect to FIG. 24, a cut may be provided to determine the Y direction overlay between the cut and the substantially vertical structure. That is, when the cutting portion and the structure are generated, a Y-direction shift occurs between them, causing the symmetry to be broken, so that the Y-direction overlay determination becomes possible.

Therefore, referring to FIG. 30C, one or more cuts are introduced into the structure of the non-product target design of FIG. 30B to enable determination of the Y-direction overlay. To make this possible, a unit cell 3050 is defined. As shown, the unit cell has structures 3030 and 3040. Furthermore, the unit cell has a cutting portion 3060 in the structure 3030. The cutting portion causes the X symmetry to be broken by the relative displacement in the Y direction between the creation of the cutting portion 3060 and the structure 3040. Accordingly, when there is a relative displacement in the Y direction between the cutting portion 3060 and the structure 3040, the cutting portion 3060 may cause asymmetry in the X direction. The cutting portion 3060 generates a reference for determining the Y-direction overlay due to a relative shift occurring therebetween while the cutting portion 3060 and the structure 3040 are being created. Since the cutting portion 3060 and the structure 3040 serve as a proxy for the structure 3010 and the cutting portion 3020, the cutting portion 3060 and the cutting portion 3060 from radiation redirected by the non-product target under relative displacement conditions Determining the relative displacement in the Y direction between the structures 3040 may correspond to an overlay in the Y direction between the structures 3010 and the cutting portion 3020.

In one embodiment, the cutout 3060 causes the unit cell to be symmetrical in the X direction in its nominal configuration. Furthermore, in one embodiment, the cutting portion 3060 does not affect the symmetry of the unit cell in the Y direction. In one embodiment, the cutout 3060 has a CD and pitch comparable to the cutout 3020 during the device patterning process, if possible. However, the size, number and location of the cuts can be adapted to create a symmetrical unit cell. In one embodiment, as shown in Fig. 30C, the unit cell is repeated as a plurality of instances to form a non-product target to be created on the substrate.

Therefore, in this embodiment, in the nominal configuration, the unit cell 3060 has both X and Y symmetry. Furthermore, if there is a relative shift in the Y direction between features, the X symmetry within the unit cell is broken (while the Y symmetry is preserved), so that the Y direction overlay can be determined.

Referring to Figure 31, an embodiment of a method for designing a non-product target is schematically shown. Several steps are described, but not all of these steps are essential. Thus, in one embodiment, a sub-combination of steps may be selected. Furthermore, the order of steps (or sub-combinations of steps) can be rearranged. Furthermore, the design method is described in terms of generating a non-product target design to determine an overlay (or any other parameter derived from the result of this target). However, this method can be extended with one or more other parameters.

At 3100, one or more non-product targets are designed in the non-product target layout design process. The one or more non-product target designs may be any one or more of those described herein. In one embodiment, one or more techniques for designing a non-product target design, as described herein, may be used. In one embodiment, the non-product target layout design process primarily determines the geometry of the unit cell of the non-product target (and thus the geometry of the non-product target).

In one embodiment, the non-product target layout design process involves evaluating device patterns to identify overlays of interest. Often, there are multiple combinations of features and/or layers for evaluating the overlay, especially in the LELE process. Therefore, it may be desirable to determine one or more overlay-critical combinations of features and/or layers.

If one or more overlays are identified for the feature/layer being evaluated and one or more directions (e.g., X, Y or X and Y), a repeating pattern (e.g., a line space pattern, e.g., of a closed curve as in FIG. Array) can be created. In one embodiment, the repeating pattern has a pitch and/or CD comparable to a feature/layer of interest from the device pattern.

Then, depending on the device pattern and overlay to be measured, the geometry of the unit cell of the non-product target design can be created using one or more of the techniques described herein. For example, if the feature of interest is parallel (e.g., in the Y direction) and an overlay in the X direction is desired, a target as in FIG. 21 can be created, or the target includes the design feature in FIG. Can be decided. For example, if the features of interest are parallel (e.g., in the Y direction) and an overlay in the Y direction is desired, a target including a cut/protrusion arrangement as in FIG. 22 can be created, or the target is It includes 22 design features to allow the overlay to be determined. For example, if the feature of interest is vertical and an overlay in the X direction is desired, a target as in FIG. 23 may be created, or the target may include the design feature in FIG. 23 to allow the overlay to be determined. For example, if the feature of interest is vertical and the overlay measurement in the Y direction is to be measured, a target as in FIG. 24 may be created, or the target may include the design feature in FIG. 24 to allow the overlay to be determined.

In appropriate cases and in many cases, the cuts/protrusions on the lines of the line space pattern can be used as a means to break the symmetry in the X and/or Y directions so that the respective overlay can be determined. In one embodiment, the cut/protrusion is compared in terms of CD and/or pitch as an associated feature in the device pattern. However, in one embodiment, the location of the cut/protrusion should be such that the unit cell is symmetrical in its nominal configuration. In one embodiment, the cut/protrusion and/or structure of the unit cell is selected to make the unit cell as small as possible.

In one embodiment, the target does not necessarily have to follow all of the process steps of the device (e.g., one or more process steps of the device may be bypassed when forming the target, for example if such steps are difficult to model. have). However, the process difference between the device and the target should not affect the overlay for the feature/layer under consideration.

If both the overlay in the X direction and the overlay in the Y direction are required for the same target, the vertical shift of the cut should not change the symmetry about the Y axis and the horizontal shift of the structure should not change the symmetry about the X axis. Then, the X and Y direction overlays help to ensure that they are decoupled when they are determined from redirected radiation from the target.

In one embodiment, if one of the layers is treated with LELE, different targets may be used to decouple the overlay from each of the lithographic steps. If two layers are treated with LELE, for example four targets can be used.

In one embodiment, overlays between three or more layers may be combined within the same target (eg, a target such as the target of FIG. 27) if the target's overlay sensitivity allows. This will improve the space-efficiency, but there may be a loss of accuracy, for example because of the more complex the target, resulting in cross-talk or inaccuracies in the modeling.

In one embodiment, the target will have a clearance area and a patterned area with a pattern of similar density to the device. In one embodiment, the clearance area around the target and the patterned area may be, for example, a clearance area of at least 0.2 μm and/or a patterned area of at least 2 μm.

Given a nominal target design, various evaluation steps may be performed to tune the nominal target design and/or determine whether the nominal target design will be suitable. Therefore, in addition to the design of the target, for example to satisfy the overlay behavior of the device feature, the design of the target is printability (e.g., the possibility that the target can be created as part of the patterning process), detectability (e.g. , How good the signal is generated by the target), robustness (e.g., how stable the target is to fluctuations occurring in the patterning process), and/or device matching (e.g., the representation of the overlay of the device is It can be analyzed in terms of how close it is to the determination of the overlay from the target).

Therefore, at 3110, device matching may be performed to determine that the overlay measured from the target represents the overlay of the device. This can be done by using a simulator or mathematical model to determine whether the simulated or modeled overlay of interest of the device matches the corresponding simulated or modeled overlay of interest of the target design. In one embodiment, matching may be performed on the lithographic step of the patterning process (eg, in-field matching). In one embodiment, matching may be performed on the etching step of the patterning process (eg, inter-field matching). If there is not enough match, the target design can be discarded or modified, for example (where the modification is a change in the pitch of a feature of the target, a change in the CD of the feature of the target, a change in the material of the structure of the target, etc.) May contain).

At 3120, a detectability evaluation can be performed to determine how well the signal is generated by the target design. This can be done by determining the expected signal from the target design using a simulator or a mathematical model, and determining whether it meets a threshold. In one embodiment, this may involve evaluating the sensitivity of the target to the overlay, such as any of the sensitivities as discussed herein (eg, Jacobian). In one embodiment, this evaluation may take into account the pupil intensity of the target design (eg, root mean square of the pupil intensity), stack sensitivity and/or diffraction efficiency, and evaluate this against a threshold. If there is not enough match, the target design can be discarded or modified, for example (where the modification is a change in the pitch of a feature of the target, a change in the CD of the feature of the target, a change in the material of the structure of the target, etc.) May contain). In one embodiment, iterations of steps 3110 and 3120 are performed until each threshold is satisfied.

At 3130, a printability evaluation can be performed to determine the likelihood that a target can be created as part of the patterning process. This can be done by using a simulator or a mathematical model to determine whether the target design will be sufficiently created on the substrate (eg, whether to pass or satisfy a threshold). If sufficient printability does not exist, the target design can, for example, be discarded or modified (where modification is a change in the pitch of the features of the target, a change in the CD of the features of the target, a change in the material of the structure of the target, etc.) May include).

At 3140, a robustness evaluation may be performed to determine how stable the target is to variations occurring in the patterning process. This can be done by using a simulator or a mathematical model to determine whether the target design is sensitive to variations occurring in the patterning process (eg, past or satisfies a threshold) and will produce inaccurate results. For example, such an evaluation can determine the orthogonality of the target result to the process perturbation, for example by introducing perturbation into the simulator or model. If sufficient robustness does not exist, the target design can be discarded or modified, for example (where modification is a change in the pitch of the features of the target, a change in the CD of the features of the target, a change in the material of the structure of the target, etc.) May include).

At 3150, a target may be created by a patterning process to verify the target. The patterning process of printing the target can be set up to direct a variety of known overlays to the target, and the target can then be measured to determine the overlay using the techniques herein. The set overlay can then be compared with the acquired overlay. If there is not enough match (e.g., past or satisfying a threshold), the target design can be discarded or modified, for example (where the modification is a change in the pitch of the features of the target, the CD of the features of the target) May include changes in the material of the target structure, etc.).

The determined patterning process parameter value (eg, overlay value) and the techniques herein can be used for several purposes. For example, the important aspects for making the patterning process possible are improving the process itself, setting it up for monitoring and control, and now actually monitoring and controlling the process itself (i.e., patterning process parameter values. To predict the likelihood of a defect on the basis of). Patterning process parameter values and techniques herein may be used in any of these aspects. Further, assuming the underlying configuration of the patterning process (such as patterning device pattern(s), resist type(s), post-lithography process steps (like development, etching, etc.)), to transfer the pattern onto the substrate. Implementing the process of setting up the device in the patterning process, developing one or more metrology targets to monitor the process, setting up the metrology process to measure the metrology target, and monitoring and/or controlling the process based on measurements. desirable. Patterning process parameter values and techniques herein may be used in any of such processes.

Although in the discussion herein one embodiment of a metrology process and metrology target designed to measure an overlay of a device being formed on a substrate will be considered, embodiments herein are intended to provide other metrology processes and targets, such as symmetrical structures. It is equally applicable to processes and targets for measuring various other asymmetries, such as inner, sidewall angle asymmetry, bottom floor tilt angle asymmetry, CD asymmetry, and the like. Therefore, referring to an overlay metrology target, overlay data, and the like in this specification should be considered to be appropriately modified so as to refer to other types of metrology processes and targets.

In one embodiment, a method of determining a parameter of a patterning process, comprising illuminating the substrate with a radiation beam such that a beam spot on the substrate is filled with one or more physical instances of a unit cell, wherein the unit cell is at a nominal value of the parameter. Has geometric symmetry -; Detecting zero-order radiation redirected by one or more physical instances of the unit cell as a main component using a detector; And determining, by a hardware computer system, a non-nominal value of the parameter of the unit cell from the value of the optical property of the detected radiation.

In one embodiment, this parameter includes an overlay. In one embodiment, the method includes determining an edge placement error based on the parameter. In one embodiment, the optical property value obtained from the pixel of the detected radiation having a greater sensitivity to the physical effect measured by the parameter is the detected radiation having a lower sensitivity to the physical effect measured by the parameter Contributes more to determining the non-nominal value of this parameter than the optical property values obtained from other pixels of. In one embodiment, the values of the optical properties form a pupil representation. In one embodiment, the value of the optical characteristic is processed to subtract the optical characteristic value across the axis of symmetry, to reduce or eliminate the optical characteristic value of the symmetric optical characteristic distribution of the detected radiation. In one embodiment, the non-nominal value of the parameter is determined using, for a plurality of pixels of detected radiation, the summation of optical characteristic values for that pixel multiplied by the associated weight for each pixel. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, one or more physical instances of the unit cell are device structures. In one embodiment, the at least one physical instance of the unit cell is a non-device structure within a substrate die containing a device structure. In one embodiment, the radiation is detected after an etching process to create one or more physical instances of the unit cell. In one embodiment, the parameter comprises an overlay, and the method further comprises determining a value of the first overlay separately from the second overlay also obtainable from the optical property value, from the same optical property value, and ,

The first overlay may be in a different orientation from the second overlay, or between portions of the unit cell in a different combination from the second overlay.

In one embodiment, a method of determining a parameter of a patterning process, comprising: obtaining a detected pupil representation of radiation redirected by a structure having geometric symmetry in a nominal physical configuration-a physical configuration different from the nominal physical configuration of the structure Results in an asymmetric optical property distribution within the pupil representation -; Processing the pupil representation to subtract an optical feature value across an axis of symmetry to reduce or eliminate the optical feature value of a symmetrical optical feature distribution in the pupil representation; And determining, by a hardware computer system, a value of the patterning process parameter based on the optical characteristic value obtained from the processed pupil representation.

In one embodiment, the patterning process parameter is an overlay, and the different physical configuration is a relative shift of at least a portion of the structure relative to another portion of the structure. In one embodiment, the pupil representation is for zero order radiation as the principal component. In one embodiment, the optical property values obtained from pixels of the processed pupil representation having a greater sensitivity for the different physical configurations are optical property values obtained from other pixels of the detected radiation having a lower sensitivity for the different physical configurations. It contributes more to determining the value of the patterning process parameter. In one embodiment, the value of the patterning process parameter is determined by using a summation of optical characteristic values for a corresponding pixel multiplied by an associated weight for each pixel for a plurality of pixels of the pupil expression. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, radiation is detected after an etching process to create the structure. In one embodiment, the step of determining comprises determining a value of the first patterning process parameter of the structure separately from the value of the second patterning process parameter, which is also obtainable from the same optical property value, from the optical property value. And the first patterning process parameter is in a different direction from the second patterning process parameter, or between portions of the structure in a different combination from the second overlay.

In one embodiment, a method of determining a parameter of a patterning process, the method comprising: obtaining a detected representation of radiation redirected by a structure having geometric symmetry in a nominal physical configuration, the detected representation of the radiation being a beam on the substrate Obtained by illuminating the substrate with a beam of radiation so that a spot is filled with the structure; And determining, by a hardware computer system, a value of the patterning process parameter based on an optical characteristic value obtained from an asymmetric optical characteristic distribution portion of the detected radiation expression having a higher weight than other portions of the detected radiation expression. The optical property distribution results from a physical configuration different from the nominal physical configuration of the structure.

In one embodiment, the patterning process parameter is an overlay, and the different physical configuration is a relative shift of at least a portion of the structure relative to another portion of the structure. In one embodiment, the detected radiation representation is a pupil representation. In one embodiment, the detected radiation was zero-order radiation as a main component. In one embodiment, the detected radiation representation is processed to subtract the optical property value across the axis of symmetry, to reduce or eliminate the optical property value of the symmetrical optical property distribution of the detected radiation representation. In one embodiment, the value of the patterning process parameter is determined using a summation of optical characteristic values for the pixel multiplied by an associated weight for each pixel for a plurality of pixels of the detected radiation representation. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, the weighting is configured such that the first type of patterning process parameter is determined for different physical configurations, independent of the second type of patterning process parameter, which is also obtainable from the same optical property value, the The first type of patterning process parameter is in a different direction from the second type of patterning process parameter, or is between portions of the unit cell in a different combination from the second type of patterning process parameter. In one embodiment, the method further comprises a weight configured to cause a second type of patterning process parameter to be determined for different physical configurations.

In one embodiment, a method of determining a parameter of a patterning process, the method comprising: obtaining a detected representation of radiation redirected by a structure having geometrical symmetry at a nominal value of the parameter, wherein the detected representation of radiation is on the substrate Obtained by illuminating the substrate with a radiation beam such that a beam spot is filled with the structure, and at a non-nominal value of the parameter, the physical configuration of the structure results in an asymmetric optical property distribution within the detected radiation representation; And by a hardware computer system, the non-nominal value of the parameter of the structure is multiplied by the associated weight for each pixel, for a plurality of pixels of the detected radiation representation, to the sum of optical characteristic values for the corresponding pixel. Determining based on-a method is provided, wherein the weights for pixels in the asymmetric optical characteristic distribution are different from the weights for pixels in the symmetric optical characteristic distribution portion of the detected radiation representation.

In one embodiment, this parameter includes an overlay. In one embodiment, the detected radiation representation is a pupil representation. In one embodiment, the detected radiation was zero-order radiation as a main component. In one embodiment, the detected radiation representation is processed to subtract the optical property value across the axis of symmetry, to reduce or eliminate the optical property value of the symmetrical optical property distribution of the detected radiation representation. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, the parameter comprises an overlay, and the weight is configured to determine a first type of overlay for the structure separately from a second type of overlay for the structure also obtainable from the same optical property value. do. In one embodiment, the method further includes a weight configured to determine, from the same optical property value, a second type of overlay for the structure separately from the first type of overlay for the structure.

In one embodiment, obtaining a detected representation of radiation redirected by a structure having geometrical symmetry in a nominal physical configuration-a physical configuration different from the nominal physical configuration of the structure is a distribution of an asymmetric optical property within the detected representation And the patterning process parameter measures a change in the physical composition; And determining, by a hardware computer system, a value of the patterning process parameter in the different physical configuration using a reconstruction process that processes optical characteristic values derived from the detected representation.

In one embodiment, the method further comprises processing the representation to subtract an optical property value across an axis of symmetry to reduce or eliminate an optical property value of a symmetrical optical property distribution within the representation, wherein the determining The step includes determining a value of the patterning process parameter using a reconstruction process that processes optical characteristic values derived from the processed detected representation. In one embodiment, the reconstruction process involves generating, using a mathematical model of the structure, a simulated representation of radiation redirected by the structure to be compared to an optical characteristic value derived from the detected representation. In one embodiment, the mathematical model is based on a profile of the structure derived from measurements of instances of the structure. In one embodiment, the reconstruction process involves comparing optical property values derived from the detected representation against a library of simulated representations of radiation redirected by the structure.

In one embodiment, obtaining a detected representation of radiation redirected by a structure having geometrical symmetry in a nominal physical configuration-a physical configuration different from the nominal physical configuration of the structure is a distribution of an asymmetric optical property within the detected representation And the patterning process parameter measures a change in the physical composition; And determining, by a hardware computer system, the value of the patterning process parameter in the different physical configuration using a nonlinear solver that processes optical characteristic values derived from the detected representation. Is provided.

In one embodiment, the nonlinear solver solves a function, and the one or more variable terms of the function are at least one variable term having the patterning process parameter as an odd-squared variable, and/or other parameters of the structure as a variable. In combination, it consists of only one or more variable terms having the patterning process parameter as a variable. In one embodiment, the method further comprises processing the expression to subtract the optical characteristic value across an axis of symmetry, to reduce or eliminate the optical characteristic value of a symmetric optical characteristic distribution within the expression, and from the processed detected expression. And determining a value of the patterning process parameter using a nonlinear solver that processes the derived optical property values.

In one embodiment, a method of configuring a parameter determination process, comprising: obtaining a mathematical model of a structure, wherein the mathematical model is configured to predict an optical response when illuminating the structure with a radiation beam, the structure being nominal Has geometric symmetry in physical configuration -; By means of a hardware computer system, in order to obtain a plurality of pixel sensitivities, a specific amount of perturbation within the physical configuration of the structure is simulated using the mathematical model to correspond to the corresponding optical response within each of a plurality of pixels. Determining a change; And determining, based on the pixel sensitivity, a plurality of weights to be combined with the measured pixel optical characteristic values of the structure on the substrate to calculate a value of a parameter associated with a change in the physical configuration, each weight being one Corresponding to the pixel of the parameter determination process comprising-is provided.

In one embodiment, the parameter is an overlay, and the different physical configuration is a relative shift of at least a portion of the structure relative to another portion of the structure. In one embodiment, the optical response includes the optical property in the form of a pupil image. In one embodiment, the optical response is for zero order radiation as a principal component. In one embodiment, determining the weights includes using a Jacobian matrix. In one embodiment, determining the weights includes using a Hessian matrix. In one embodiment, determining the weights includes using a Moore-Penrose pseudo-inverse matrix. In one embodiment, the weight is a sum of optical characteristic values for a corresponding pixel multiplied by the weight among a plurality of weights associated with each pixel for a plurality of pixels of the detected radiation expression. It is structured so that it can be determined using. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, the method further comprises determining a set of measurement settings for obtaining the measured pixel optical characteristic values, wherein the set of measurement settings corresponds to the plurality of weights. In one embodiment, the set of measurement settings comprises among a plurality of optical property readings taken by the detector sensor of the wavelength of the measurement beam, the polarization of the measurement beam, the dose of the measurement beam, and/or of a particular illumination of the structure. Contains one or more selected. In one embodiment, the step of obtaining the mathematical model comprises performing a CD measurement on one or more substrates containing the structure and obtaining a nominal profile of the structure for perturbation of the physical configuration of the structure. And calibrating the model to the CD measurement. In one embodiment, the method comprises the steps of measuring an optical property value of radiation redirected by a plurality of structures having different known physical configurations and associated expected values of the parameters; Combining the weights and measured optical property values to determine a value of the parameter for each of the known different physical configurations; And evaluating the determined value of the parameter as an expected value of the parameter. And in response to the evaluation, adjusting a parameter of the mathematical model and/or adjusting one or more of the weights.

In one embodiment, predicting, by a hardware computer system, an optical response when illuminating the structure with a radiation beam using a mathematical model of the structure-the structure has geometric symmetry in its nominal physical configuration, and the patterning process parameter Measures the change in the physical composition -; And determining, by the hardware computer system, a coefficient of a mathematical function of the patterning process parameter as a variable, based on the optical response, using a nonlinear solver, the determined coefficient and the function in the detected representation. In a physical configuration different from the nominal physical configuration, resulting in a characteristic distribution, used in conjunction with a measured representation of the detected radiation from the structure on a substrate to determine the value of the patterning process parameter for the measured structure. To do, a method is provided. In one embodiment, the method includes the step of determining a corresponding change in the optical response by simulating a specific amount of perturbation within the physical configuration of the structure using the mathematical model, and determining the coefficient Use a modified optical response. In one embodiment, the method comprises obtaining a detected representation of radiation redirected by the structure on the substrate, having the different physical configuration, and processing an optical property value derived from the detected representation and the Using a nonlinear solver using the determined coefficients, determining a value of the patterning process parameter. In one embodiment, the nonlinear solver solves a function, and the one or more variable terms of the function are at least one variable term having the patterning process parameter as an odd-squared variable, and/or other parameters of the structure as a variable. In combination, it consists of only one or more variable terms having the patterning process parameter as a variable. In one embodiment, the method further comprises processing the optical response to subtract an optical property value across an axis of symmetry to reduce or eliminate an optical property value of a symmetrical optical property distribution within the optical response, the method further comprising: The step of determining the coefficient is based on an optical property value derived from the processed optical response. In one embodiment, the mathematical model obtains the nominal profile of the structure using the nominal profile of the structure derived from calibration of the CD measurement of the mathematical model. In one embodiment, the coefficient comprises a set of coefficients for each of a plurality of pixels in the optical response.

In one embodiment, obtaining measurement results for different instances of the structure produced by the patterning process-the measurement results are obtained at each of a plurality of different set values of a patterning process parameter measuring a change in the physical composition of the structure, , Each different set value of the patterning process parameter corresponds to a physical configuration of the structure, resulting in an asymmetric optical property distribution within the radiation representation; And determining, by a hardware computer system, a plurality of data-drive values corresponding to weights to be combined with the measured optical characteristic values of the additional instance of the structure to calculate the value of the patterning process parameter, the setting. A method is provided, comprising the value and measurement result being used in an objective function or merit function or machine learning algorithm to determine the data-driven value.

In one embodiment, the method comprises modifying a mathematical model of the structure using the determined data-driven value, and being combined with the measured optical property values of the additional instance of the structure using the mathematical model. It further includes the step of inducing a weight for. In one embodiment, the method further includes updating a value of a nominal profile of the structure implemented in the mathematical model using a Hessian matrix of the mathematical model. In one embodiment, the method further comprises calculating a weight for combining with the measured optical characteristic values of the additional instances of the structure using the Hessian matrix of the modified mathematical model. In one embodiment, the measurement result is a plurality of detected representations of radiation redirected by different instances of the structure. In one embodiment, the detected representation of the radiation was obtained by illuminating the substrate with a radiation beam such that a beam spot on the substrate is filled with the structure. In one embodiment, the method further comprises generating one or more composite representations of radiation expected to be redirected by an instance of the structure and expected for variations in the patterning process, the plurality of data-driven Determining a value is based on the set value, the measurement result and the one or more composite representations. In one embodiment, the one or more composite representations of radiation are generated using a Hessian matrix of the mathematical model. In one embodiment, one or more composite representations of the radiation are generated using nonlinear simulations. In one embodiment, the patterning process parameter is an overlay. In one embodiment, the method comprises determining a value of the patterning process parameter for an additional instance of the structure based on the plurality of weights by combining the measured optical property value of the additional instance of the structure. Include more. In one embodiment, each of the measured optical characteristic values corresponds to one pixel in a pupil expression, and the method includes, for a plurality of pixels of the pupil expression, the value of the patterning process parameter for the additional instance. Determining based on the summation of the measured optical characteristic values for the corresponding pixel multiplied by the associated weight for the pixel, wherein the weight for the pixel in the asymmetric optical characteristic distribution portion of the pupil expression is It is different from the weights for the pixels in the symmetrical optical characteristic distribution part.

In one embodiment, a method of determining a parameter of a patterning process, the method comprising: obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell, wherein the unit cell has geometric symmetry in a nominal value of the parameter, The detected representation of the radiation is obtained by illuminating the substrate with a radiation beam such that a beam spot on the substrate is filled with one or more physical instances of the unit cell; And a first type of parameter for the unit cell, apart from the second type of parameter for the unit cell, also obtainable from the same optical characteristic value, by a hardware computer system and from an optical characteristic value from the detected radiation representation. Determining the value of the parameter, wherein the first type of parameter is in a different direction from the second type of parameter or between portions of the unit cell in a combination different from the second type of parameter, an overlay determination method is provided. do.

In one embodiment, this parameter includes an overlay. In one embodiment, the first and first type of parameters are for different directions and for the same first and second parts of the unit cell. In one embodiment, the first type of parameter is between portions of a unit cell in a different combination than the second type of parameter. In one embodiment, the method further comprises determining a value of the second type of parameter from the same optical characteristic value as the value of the first type of parameter is determined. In one embodiment, determining the value of the first type of parameter uses a set of weights for the pixel optical characteristic values. In one embodiment, the value of the parameter of the first type is determined using the sum of optical characteristic values for the pixel, multiplied by the associated weight for each pixel, for a plurality of pixels of the detected radiation representation. In one embodiment, the optical characteristic value obtained from a pixel of the detected radiation representation having a greater sensitivity to the physical effect measured by the parameter is a detected optical property value having a lower sensitivity to the physical effect measured by the parameter. It contributes more to determining the value of the first type of parameter than the values of optical properties obtained from other pixels of radiation. In one embodiment, the detected radiation was zero-order radiation as a main component. In one embodiment, the detected radiation representation is a pupil representation. In one embodiment, the detected radiation representation is processed to subtract the optical property value across the axis of symmetry, to reduce or eliminate the optical property value of the symmetrical optical property distribution of the detected radiation representation. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, the detected radiation representation was detected after an etching process to create the structure.

In one embodiment, a method of determining a parameter of a patterning process, the method comprising: obtaining a detected representation of radiation redirected by one or more physical instances of a unit cell, wherein the unit cell has geometric symmetry in a nominal value of the parameter, The detected representation of the radiation is obtained by illuminating the substrate with a radiation beam such that a beam spot on the substrate is filled with one or more physical instances of the unit cell; And from the optical property values from the radiation representation detected and by the hardware computer system, the value of the parameter with respect to the first portion of the unit cell and the second portion of the unit cell, with a second portion of the unit cell. An overlay comprising the step of determining separately from the value of the parameter also obtainable from the same optical property value, between a third portion of the unit cell or between a third portion of the unit cell and a fourth portion of the unit cell. A method of determination is provided.

In one embodiment, this parameter includes an overlay. In one embodiment, the method comprises, from the optical property value, between the second and third portions of the unit cell or each unit cell, or between the third and fourth portions of the unit cell or each unit cell. Further comprising determining a value of the parameter for to be separate from the value of the parameter for the unit cell or between the first portion and the second portion of each unit cell. In one embodiment, determining the parameter value uses a set of weights for pixel optical characteristic values. In one embodiment, the parameter value is determined using a summation of optical characteristic values for the pixel, multiplied by the associated weight for each pixel, for a plurality of pixels of the detected radiation representation. In one embodiment, the optical characteristic value obtained from a pixel of the detected radiation representation having a greater sensitivity to the physical effect measured by the parameter is a detected optical property value having a lower sensitivity to the physical effect measured by the parameter. It contributes more to determining the value of this parameter than the optical property values obtained from other pixels of the radiation representation. In one embodiment, the detected radiation was zero-order radiation as a main component. In one embodiment, the detected radiation representation is a pupil representation. In one embodiment, the detected radiation representation is processed to subtract the optical property value across the axis of symmetry, to reduce or eliminate the optical property value of the symmetrical optical property distribution of the detected radiation representation. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure. In one embodiment, radiation is detected after an etching process to create the structure.

In one embodiment, a method of configuring a parameter determination process, comprising: obtaining a mathematical model of a structure on a substrate, the model being configured to predict an optical response when illuminating the structure with a radiation beam, the structure being nominal Has geometric symmetry in parameter values -; By means of a hardware computer system, using the model, a change in a parameter of a first type of the structure is simulated to determine a corresponding first change in the optical response in each of a plurality of pixels, and a change in a parameter of a second type Simulating to determine a corresponding second change in the optical response within each of a plurality of pixels-the parameter of the first type is a direction different from the parameter of the second type or a part of the structure that is different from the parameter of the first type Between different combinations of -; And based on the first change and the second change in the optical response, the measured pixel optical characteristic value to calculate a value of the first type of parameter obtained from the same measured optical characteristic value independently of the first type of parameter. A method of configuring a parameter determination process is provided, including determining a plurality of weights to be combined with.

In one embodiment, this parameter includes an overlay. In one embodiment, the plurality of weights for the first type of parameter is an orthogonal of a vector corresponding to a change of the second type of parameter in terms of a second change in the optical response of the plurality of pixels. A method of constructing a parameter determination process is provided, which is determined using the result of a backside projection of a vector corresponding to a change in a parameter of the first type in terms of a first change in the optical response of the plurality of pixels. In one embodiment, the method, based on the first change and the second change in the optical response, calculate a value of a second type of parameter obtained from the measured optical characteristic value separately from the first type of parameter So as to further include determining a plurality of weights to be combined with the measured pixel optical characteristic values. In one embodiment, the plurality of weights for the parameters of the second type are for orthogonal lines of vectors corresponding to the change of the parameters of the first type in terms of the first change in the optical response of the plurality of pixels, It is determined using the result of the backside projection of the vector corresponding to the change in the parameter of the second type in terms of the second change in the optical response of the plurality of pixels. In one embodiment, the weight is a corresponding pixel in which the first type parameter and/or the second type parameter is multiplied by an associated weight for each pixel for a plurality of pixels of the detected radiation expression. Is configured to be determined using the summation of the optical property values for. In one embodiment, the optical response includes the optical property in the form of a pupil image. In one embodiment, the optical response is for zero order radiation as a principal component. In one embodiment, the optical properties are intensity and/or phase. In one embodiment, the structure is a device structure. In one embodiment, the structure is a non-device structure in a substrate die containing a device structure.

In one embodiment, a first structure configured to be created by a first patterning process; And a second structure configured to be produced by the second patterning process, wherein the first structure and/or the second structure are not used to create a functional aspect of the device pattern, and the first and second structures The structures together form one or more instances of the unit cells, the unit cells having geometric symmetry in their nominal physical configuration, and the unit cells being the relative of the pattern placement in the first patterning process, the second patterning process and/or other patterning process In a physical configuration different from the nominal physical configuration due to the shift, a metrology target is provided having features that cause asymmetry within the unit cell.

In one embodiment, the first structure comprises a structure of a first dimension and/or material, and the second structure comprises a structure of a second dimension or material, and the feature comprises a structure of the second dimension and/or material. And the first dimension and/or material different from. In one embodiment, the first structure comprises a structure arranged in an array in a first direction, and at least one such structure is arranged along a second direction substantially perpendicular to the first direction, separated by a void And/or the second structure comprises a structure arranged in an array in a first direction, at least one such structure having a second direction substantially perpendicular to the first direction. Thus, it comprises a plurality of sub-structures arranged, separated by voids, the features comprising voids of the first structure and/or the second structure. In one embodiment, voids in the first structure and/or the second structure are created using a different patterning process than the first and second patterning processes. In one embodiment, the first structure includes the void, and the second structure includes the void. In one embodiment, the voids of the first structure have a different pitch than the voids of the second structure. In one embodiment, in a nominal physical configuration, at least one void of the first structure is aligned with at least one void of the second structure. In one embodiment, the first structure includes a closed curve structure, and the second structure includes a closed curve structure. In one embodiment, the structures are arranged in a first array in a direction substantially perpendicular to a direction in which the structures are arranged in a second array or the structures are arranged in a third array of the structures.

In one embodiment, a computer program product is provided comprising a non-transitory computer-readable medium having a data structure recorded thereon, the data structure corresponding to a metrology target as described herein. In one embodiment, a reticle comprising a pattern corresponding to a metrology target as described herein is provided.

In one embodiment, creating a first structure for the metrology target, the first structure will be created by a first patterning process that creates a corresponding device feature of the device; Creating a second structure for the metrology target-a second structure will be created by a second patterning process that creates a corresponding additional device feature of the device, wherein the first structure and the second structure are one of the unit cells. Forming instances of the above together, the unit cells having geometric symmetry in their nominal physical configuration; And introducing a feature into the metrology target that causes an asymmetry in a unit cell in a physical configuration different from the nominal physical configuration due to a relative shift of the position of the device feature in the device from the expected position of the device feature in the device. A method of incorporating is provided.

In one embodiment, the features of the first structure have substantially the same dimensions and/or pitch as the corresponding features of the device, and/or the features of the second structure are substantially the same as the corresponding features of the device. Have dimensions and/or pitches. In one embodiment, the feature in the metrology target results in a first type of asymmetry in the unit cell for a relative shift in a first direction, and a different second in the unit cell for a relative shift in a different second direction. It results in type asymmetry. In one embodiment, the method comprises at least one selected from printability of the measurement target, detectability of the measurement target, robustness of the measurement target to process variation, and/or matching of the measurement target to a device pattern. It further includes the step of evaluating. In one embodiment, the method includes repeatedly evaluating the matching of the metrology target with the device pattern and detectability of the metrology target.

In one embodiment, a method is provided that includes measuring radiation redirected by metrology as described herein transferred to a substrate using a patterning process to determine a value of a parameter of the patterning process. In one embodiment, the parameters include overlay and/or edge placement errors.

Referring to FIG. 32, a computer system 3200 is shown. Computer system 3200 includes a bus 3202 or other communication mechanism for communicating information, and a processor 3204 (or several processors 3204 and 3205) coupled with the bus 3202 to process the information. Computer system 3200 includes main memory 3206, such as random access memory (RAM) or other dynamic storage device, coupled to bus 3202 to store information and instructions to be executed by processor 3204. The main memory 3206 may also be used to store temporary variables or other intermediate information while an instruction to be executed by the processor 3204 is being executed. The computer system 3200 provides static information about the processor 3204. And a read-only memory (ROM) 3208 or other static storage device coupled to the bus 3202 for storing instructions. A storage device 3210 such as a magnetic disk or optical disk is provided and information is provided. And to bus 3202 to store instructions.

Computer system 3200 may be coupled via bus 3202 to a display 3212, such as a cathode ray tube (CRT) or flat panel or touch panel display, to display information to a computer user. An input device 3214 comprising alphanumeric keys and other keys is coupled to the bus 3202 to communicate information and command selection to the processor 3204. Another type of user input device is a cursor control 3216, such as a mouse, trackball, or cursor direction key, for communicating instructional information and command selection to the processor 3204 and controlling cursor movement on the display 3212. . Such input devices typically have two degrees of freedom in two axes, a first axis (eg x) and a second axis (eg y), allowing the device to specify its position in a plane. A touch panel (screen) display may be used as an input device.

Computer system 3200 may be adapted to perform functions herein as a processing unit in response to processor 3204 executing one or more sequences of one or more instructions stored in main memory 3206. These instructions may be read into main memory 3206 from another computer-readable medium, such as storage device 3210. Executing a sequence of instructions contained in main memory 3206 causes processor 3204 to perform the processes described herein. One or more processors in a multiple processing unit may be employed to execute a sequence of instructions contained in main memory 3206. In other embodiments, wired circuitry may be used instead of or in combination with software instructions. Thus, embodiments are not limited to any particular combination of hardware circuitry and software.

The term "computer-readable medium" as used herein refers to any tangible medium that participates in providing instructions to processor 3204 to be executed. Such media may take many forms including, but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks such as storage device 3210. Volatile media includes dynamic memory such as main memory 3206. Transmission media includes coaxial cables, copper wiring, and fiber optics including wires including bus 3202. Transmission media may take the form of sound or light waves such as those generated during radio frequency (RF) and infrared (IR) data communications. Common types of computer-readable media are, for example, floppy disks, flexible disks, hard disks, magnetic tapes, and any other magnetic media, magneto-optical media, CD-ROMs, DVDs, any other optical media. , Punch card, paper tape, any other physical medium with a pattern of holes, RAM, PROM, and EPROM, FLASH EPROM, any other memory chip or cartridge, carrier to be described below, or any other computer readable Includes the medium.

Various types of computer-readable media may be involved in carrying one or more sequences of one or more instructions to the processor 3204 for execution. For example, the instructions may initially be held on the magnetic disk of the remote computer. The remote computer can load instructions into its dynamic memory and send the instructions over the phone line using a modem. A modem, held locally in computer system 3200, receives data on the telephone line and converts this data into infrared signals using an infrared transmitter. An infrared detector coupled to the bus 3202 may receive data carried in the infrared signal and load this data onto the bus 3202. Bus 3202 carries data to main memory 3206, from which processor 3204 retrieves and executes instructions. Instructions received from main memory 3206 may be optionally stored in storage device 3210 prior to or after execution by processor 3204.

Computer system 3200 may further include a communication interface 3218 coupled to bus 3202. Communication interface 3218 provides two-way data communication coupling to network link 3220 connected to local network 3222. For example, the communication interface 3218 may be an integrated services digital network (ISDN) card or modem for providing a data communication connection to a corresponding type of telephone line. As another example, communication interface 3218 may be a local area network (LAN) card for providing a data communication connection to a compatible LAN. A wireless link may be implemented. In any of these implementations, communication interface 3218 transmits and receives electrical, electromagnetic or optical signals carrying digital data streams representing various types of information.

Network link 3220 typically provides data communication to other data devices over one or more networks. For example, network link 3220 may provide a connection via local network 3222 to data equipment operated by host computer 3224 or Internet service provider (ISP) 3226. ISP 3226 now provides data communication services through a worldwide packet data communication network, now commonly referred to as "Internet 3228". Both the local network 3222 and the Internet 3228 use electrical, electromagnetic or optical signals to carry digital data streams. Signals passing through various networks, carrying digital data to or from computer system 3200, and signals passing through network link 3220 and through communication interface 3218, are exemplary forms of carrier waves that carry information. admit.

Computer system 3200 may transmit messages and receive data, including program code, via network(s), network link 3220, and communication interface 3218. In the example of the Internet, server 3230 may transmit the requested code for an application program over the Internet 3228, ISP 3226, local network 3222, and communication interface 3218. According to one or more embodiments, such one downloaded application provides, for example, the method disclosed herein. The received code may be executed by the processor 3204 when received, and/or stored in the storage device 3210, or other non-volatile storage for later execution. In this way, the computer system 3200 can obtain the application code in the form of a carrier wave.

For example, embodiments of the present invention include a computer program comprising one or more sequences of machine-readable instructions describing a method as disclosed herein, or a data storage medium (e.g., a semiconductor memory, a magnetic disk) in which such a computer program is stored. Or it can take the form of an optical disc). Furthermore, machine-readable instructions can be implemented in two or more computer programs. Two or more computer programs may be stored in one or more different memories and/or data storage media.

Any of the controllers described herein may be operated individually or in combination when one or more computer programs are read by one or more computer processors located within at least one component of the lithographic apparatus. The controllers may have any configuration suitable for receiving, processing, and transmitting signals, respectively or in combination. The one or more processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors for executing a computer program comprising machine-readable instructions for the methods described above. The controller may include a data storage medium for storing such a computer program, and/or hardware for receiving such a medium. Therefore, the controller(s) can operate according to machine readable instructions of one or more computer programs.

Although the text specifically mentions the use of metrology devices in the manufacture of ICs, the measurement devices and processes described herein have different applications, such as the manufacture of integrated optical systems, induction and detection patterns for magnetic field domain memories, flat panel displays. , Liquid crystal display (LCD), thin film magnetic head, and the like. Those skilled in the art, in the context of these other applications, the use of any term such as "wafer" or "die" as used herein may be considered synonymous with more general terms such as "substrate" or "target part", respectively. You will understand. The substrate herein may be processed before or after exposure, for example in a track (a tool that typically applies a layer of resist to the substrate and develops the exposed resist), a metrology tool and/or one or more of various other tools. . To the extent applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, since the substrate may be processed a plurality of times to create a multilayer integrated circuit, for example, the term substrate used herein may refer to a substrate including layers that have already been processed several times.

Although specifically mentioned above the use of embodiments of the present invention in the context of optical lithography, the present invention may also be used in other applications, for example nanoimprint lithography, and with optical lithography if the context permits. It will be appreciated that it is not limited. In the case of nanoimprint lithography, the patterning device is an imprint template or mold.

As used herein, the terms “radiation” and “beam” include ultraviolet (UV) radiation (e.g., having a wavelength of about 365, 355, 248, 193, 157, or 126 nm) and extreme ultraviolet (EUV) radiation ( For example, having a wavelength in the range of 5-20 nm), and all types of electromagnetic radiation, including particle beams such as ion beams or electron beams.

As used herein, the term “lens” may refer to any or combination of various types of optical components, including refractive, diffractive, reflective, magnetic, electromagnetic, and electrostatic optical components, if context permits. .

In this specification, passing or passing through a threshold means something that has a value that is less than a certain value or less than a certain value, something that is higher than a certain value or more than a certain value, for example, ranks higher or lower than others based on a parameter, etc. It can contain something that has been (for example, through sorting).

In this specification, the correction or correction of the error includes removing the error or reducing the error within a tolerance range.

The terms “optimizing” and “optimization”, as used herein, are a result of a lithographic or patterning process and/or a more desirable property, such as a higher accuracy of the projection of a design layout on a substrate, Refers to or refers to adjusting the lithographic apparatus, patterning process, etc. to have better properties, such as a larger process window or the like. Thus, the terms "optimizing" and "optimization" as used herein, when compared to an initial set of one or more values for one or more variables, in at least one related metric, improvement, example Refers to or refers to the process of identifying one or more values for one or more such variables, for example providing a local optimal value. "Optimal" and other related terms are to be interpreted accordingly. In one embodiment, the optimization step may be applied iteratively to provide additional improvements in one or more metrics.

In the optimization process of a system, the figure of merit of the system or process can be expressed as a function of cost. The optimization process is the process of finding a set of parameters (design variables) of a system or process that optimizes (eg minimizes or maximizes) a cost function. The cost function can take any suitable form depending on the goal of the optimization. For example, the cost function may be a weighted root mean square (RMS) of the variance of a particular characteristic (evaluation point) of the system or process relative to the intended value (eg, an ideal value) of this characteristic; The cost function may also be the largest of these variances (eg worst case variance). In this specification, the term "evaluation point" should be interpreted broadly to include any characteristic of a system or process. The design parameters of the system or process may be limited to a finite range and/or may be interdependent because of the practicality of the implementations of the system. In the case of a lithographic apparatus or device manufacturing process, these constraints are often associated with the physical properties and properties of the hardware, such as the tunable range, and/or patterning device manufacturability design rules, where the evaluation point is on the resist on the substrate. Physical points, and non-physical properties such as dose and focus.

Although specific embodiments of the present invention have been described above, it will be understood that the present invention may be practiced differently than described. For example, an embodiment of the present invention is a computer program comprising one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g., a semiconductor memory, a magnetic disk or an optical disk) in which such a computer program is stored. ) Can take the form.

In the block diagram, the illustrated components are shown as discrete functional blocks, but embodiments are not limited to a system in which the functionality described herein is organized as shown. Functionality provided by each of the components may be provided by software or hardware modules organized differently from those shown in the drawings, for example, such software or hardware may be intermixed, co-coupled, duplicated, separated, distributed (e.g. For example, it can be organized within a data center or geographically), or otherwise. The functionality described herein may be provided by one or more processors of one or more computers executing code stored on a tangible non-transitory machine-readable medium. In some cases, third-party content delivery networks may host some or all of the information delivered across the networks, in which case the extent to which the information (e.g., content) is said to be supplied or otherwise provided. In, such information is provided by sending a command to retrieve the information from the content delivery network.

Unless expressly stated otherwise, as will be apparent from this specification, descriptions utilizing terms such as “processing” “calculating” “calculating” “determining” and the like throughout the specification may be used as a special purpose computer or similar special purpose electronic processing/calculation device. It is to be understood that such as refers to an operation or process of a particular device.

The reader should understand that the present invention describes several inventions. Rather than separating such inventions into multiple separate patent applications, applicants have grouped these inventions into a single document, because their related technical gist can have its own economics in the filing process. However, the distinct advantages and aspects of these inventions should not be combined. In some cases, the embodiments solve all of the defects not pointed out herein, but these inventions are useful independently, and some embodiments solve only a subset of these problems, or are clearly understood by those skilled in the art who have reviewed this specification. It should be understood that it provides other advantages not mentioned to be mentioned. Due to cost constraints, some inventions disclosed herein are not claimed as is, but may be claimed in subsequent applications, such as continuing applications, or by amendment of the current claims. Similarly, because of space constraints, the Summary of this specification and the Summary section of the invention should not be considered as including an extensive listing of all such inventions or all aspects of such inventions.

The detailed description and drawings are not intended to limit the present invention to the specific form disclosed, and vice versa, include all modifications, equivalents, and alternative examples falling within the spirit and scope of the present invention as defined in the appended claims. It should be understood that it is intended to do.

Variations and alternative embodiments of various aspects of the present invention will become apparent to those skilled in the art upon reference to this specification. Accordingly, these detailed descriptions and drawings are for illustrative purposes only and should be construed to inform those skilled in the art of a general manner of practicing the invention. It should be understood that the aspects of the invention shown and described herein are to be considered as examples of embodiments. As will become apparent to those skilled in the art with the advantages of the detailed description of the present invention, elements and materials may replace those illustrated and described herein, parts and processes may be reversed or omitted, and certain features may be independent. It can be utilized as, embodiments or features of the embodiments can be combined. Elements described herein may be changed without departing from the spirit and scope of the invention as described in the claims that follow. Footnotes in the present specification are for convenience only and are not meant to limit the scope of the present invention.

As used throughout this specification, the word “may” is not used in a compulsory sense (ie, means must), but in an acceptable sense (ie, means there is a possibility). The words "comprising", "comprising", "comprising", and the like mean including but not limited to. As used throughout this specification, the singular forms “a” “an” and “it” include a plurality of reference members unless the context clearly indicates otherwise. Thus, for example, referring to "an" element or "a" element, there are different terms and phrases for one or more elements, such as "one or more", but a combination of two or more elements. Include. The term “or” is non-exclusive, ie, encompasses both “and” and “or” unless indicated otherwise. Terms describing conditional relationships, such as "Y in response to X", "For X, if Y", "If X, if Y," "If X, then Y", etc. It encompasses causal relationships, which are necessities and conditions of, the retreat is a sufficient causal condition, or the predecessor is a constributory. For example, "When condition Y is achieved, state X occurs" It is a generic term for "X occurs only in the case of Y" and "X occurs" in the case of Y and Z. This conditional relationship is not limited to the outcome immediately following what the retreat is achieved, since some outcomes may be delayed, and in conditional statements, the retreat is linked to its outcome, e. Related. A statement that a plurality of attributes or functions map to a plurality of objects (e.g., one or more processors performing steps A, B, C, and D) means that all such attributes or functions are Both being mapped to an object and that a subset of attributes or functions are mapped to a subset of attributes or functions (e.g., that all processors each perform step AD, and processor 1 performs step A and , Processor 2 performs some of steps B and C, and when processor 3 performs some of steps C and D). Furthermore, unless otherwise indicated, a statement that one value or action is "based on" another condition or value means that the condition or value is the only factor and when the condition or value is one of several factors. It covers both. Unless otherwise indicated, a statement that "each" instance of some collection has some properties should not be construed as excluding cases where otherwise identical or similar elements of some of the larger collections do not have such properties. That is, each does not necessarily mean each and all.

To the extent that certain U.S. patents, U.S. patent applications, or other documents (e.g., materials) are incorporated by reference, these U.S. patents, U.S. patent applications, and other documents are not included between these documents and the statements and drawings mentioned herein. It is incorporated herein by reference to the extent that no conflict exists. In the event of such conflict, any such conflicting content in such US patents, US patent applications, and other documents incorporated herein by reference is not specifically incorporated herein by reference.

The above description is provided by way of illustration and not limitation. Accordingly, it will be apparent to those skilled in the art that the invention as described may be modified without departing from the scope of the claims set forth below.

Claims (41)

As a method of determining the overlay of the patterning process,
Obtaining a detected representation of radiation redirected by one or more physical instances of the unit cell, wherein the unit cell has geometric symmetry at the nominal value of the overlay, and the detected representation of the radiation is such that the beam spot on the substrate is Obtained by illuminating the substrate with a beam of radiation to be filled with one or more physical instances of the cell; And
Determining the value of the first overlay for the unit cell, apart from the second overlay for the unit cell, also obtainable from the same optical property value, by the hardware computer system and from the optical property value from the detected radiation representation. Wherein the first overlay is in a different direction from the second overlay or between portions of the unit cell in a different combination than the second overlay. The method of claim 1,
The first and second overlays are for different directions and are for the same first and second portions of the unit cell. The method of claim 1,
The first overlay is between portions of the unit cell in a different combination than the second overlay. The method according to any one of claims 1 to 3,
The above method,
And determining the second overlay from the same optical property value as the first overlay value was determined. The method according to any one of claims 1 to 3,
The determining of the first overlay value comprises using a set of weights for pixel optical property values. The method according to any one of claims 1 to 3,
The first overlay value is determined using a summation of optical characteristic values for a corresponding pixel multiplied by an associated weight for each pixel for a plurality of pixels of the detected radiation representation. The method according to any one of claims 1 to 3,
Optical property values obtained from pixels of the detected radiation representation having a greater sensitivity to the overlay are used to determine the first overlay value than optical property values obtained from other pixels of the detected radiation having a lower sensitivity to the overlay. Contributing more to, how to determine the overlay. The method according to any one of claims 1 to 3,
The detected radiation is the zero-order radiation as a main component, the overlay determination method. The method according to any one of claims 1 to 3,
The detected radiation expression is a pupil expression. The method according to any one of claims 1 to 3,
Wherein the detected radiation representation is processed to subtract an optical property value across an axis of symmetry, to reduce or eliminate an optical property value of a symmetrical optical property distribution of the detected radiation representation. The method according to any one of claims 1 to 3,
Wherein the optical property is intensity and/or phase. The method according to any one of claims 1 to 3,
The one or more physical instances of the unit cell are device structures. The method according to any one of claims 1 to 3,
Wherein the at least one physical instance of the unit cell is a non-device structure within a substrate die containing a device structure. The method according to any one of claims 1 to 3,
Wherein the detected radiation representation is detected after an etching process to create one or more physical instances of the unit cell. As a method of determining the overlay of the patterning process,
Obtaining a detected representation of radiation redirected by one or more physical instances of the unit cell, wherein the unit cell has geometric symmetry at the nominal value of the overlay, and the detected representation of the radiation is such that the beam spot on the substrate is Obtained by illuminating the substrate with a beam of radiation to be filled with one or more physical instances of the cell; And
The overlay value between the first portion of the unit cell and the second portion of the unit cell, from the optical property value from the detected radiation representation and by the hardware computer system, is obtained from the second portion of the unit cell and of the unit cell. Determining separately from the overlay also obtainable from the same optical property value, between a third portion or between a third portion of the unit cell and a fourth portion of the unit cell. The method of claim 15,
The above method,
From the optical property value, an overlay value between the second part and the third part of the unit cell or each unit cell or between the third part and the fourth part of the unit cell or each unit cell is obtained, the unit cell or Further comprising determining separately from the overlay between the first portion and the second portion of each unit cell. The method of claim 15 or 16,
The determining of the overlay value comprises using a set of weights for pixel optical property values. The method of claim 15 or 16,
The overlay value is determined using a summation of optical characteristic values for a corresponding pixel multiplied by an associated weight for each pixel for a plurality of pixels of the detected radiation representation. The method of claim 15 or 16,
Optical property values obtained from pixels of the detected radiation representation having a greater sensitivity to the overlay are used to determine the overlay values than those obtained from other pixels of the detected radiation representation that have a lower sensitivity to the overlay. Contributing more, how to determine the overlay. The method of claim 15 or 16,
The detected radiation is the zero-order radiation as a main component, the overlay determination method. The method of claim 15 or 16,
The detected radiation expression is a pupil expression. The method of claim 15 or 16,
Wherein the detected radiation representation is processed to subtract an optical property value across an axis of symmetry, to reduce or eliminate an optical property value of a symmetrical optical property distribution of the detected radiation representation. The method of claim 15 or 16,
Wherein the optical property is intensity and/or phase. The method of claim 15 or 16,
The one or more physical instances of the unit cell are device structures. The method of claim 15 or 16,
Wherein the at least one physical instance of the unit cell is a non-device structure within a substrate die containing a device structure. The method of claim 15 or 16,
The radiation is detected after an etching process to create one or more physical instances of the unit cell. delete delete delete delete delete delete delete delete delete delete As an inspection device for inspecting an object of a patterning process,
The testing device is operable to perform the method of any one of claims 1 to 3. A computer-readable recording medium on which instructions are recorded, comprising:
A computer-readable recording medium, wherein the instructions, when executed by a computer, implement the method of any one of claims 1 to 3. As a system,
Hardware processor system; And
A non-transitory computer-readable storage medium configured to store machine-readable instructions,
The system, when executed, the machine-readable instructions cause the hardware processor system to execute the method of any one of claims 1 to 3. As a system,
An inspection device configured to provide a radiation beam to the surface of the object at an oblique angle to the surface of the object and to detect radiation scattered by physical features on the surface of the object; And
A system comprising the computer readable recording medium of claim 38. The method of claim 40,
The system further comprises a lithographic apparatus, the lithographic apparatus comprising:
A support structure configured to hold the patterning device to modulate the radiation beam, and a projection optical system arranged to project the modulated beam onto the radiation-sensitive substrate,
Wherein the object is a patterning device.

Images